antoanthongtin end

8/13/2019 AnToanThongTin End

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t r n h o t o

cc

GIO TRNH

AN TON H THNG THNG TIN


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MC LC

MC TRANG

1. LI TA ........................................................................................................... 3

2. GII THIU V M UN MN HC ................................................................ 5

3. S QUAN H THEO TRNH T HC NGH ............................................. 6

4.CC HNH THC HC TP CHNH TRONG M UN/MN HC ................... 8

5. BI 1: PHN TCH CC NGUYNNHN DN N MT AN TON TRONG

H THNG THNG TIN................................................................................... 96.BI 2:L U TR H THNG THNG TIN TRN CC THIT B L U TR .... 17

7.BI 3:VIRUS TIN HC V CCH PHNG CHNG ......................................... 49

8.BI 4:MT S BIN PHP AN TON CHO CC H THNG MY TNH ...... 58

9.BI 5:MT S PH NG THC M HOV GII M D LIU ................... 68

10.BI 6: XY DNG K HOCH BO V H THNG THNG TIN TRN

MY TNH ........................................................................................................ 80

11.TI LIU THAM KHO..................................................................................... 100


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BI 1Tn bi: PHN TCH CC NGUYN NHN DN N MT AN TON TRONG H

THNG THNG TIN

Gii thiu :Khi ni n an ton thng tin (ATTT), iu u tin ng i ta th ng ngh n l xy dngt ng la (Firewall) hoc mt ci g t ng t ngn chn cc cuc tn cng v xmnhp bt hp php. Cch tip cn nh vy khng hon ton ng v bn cht ATTT khngn thun ch l s dng mt s cng c hoc mt vi gii php no m m bo ATTT cho mt h thng cn c mt ci nhn tng qut v khoa hc hn. Mc tiu thc hin: - Xc nh tt c nhng nguyn nhn dn n d liu trn my tnh b mt - Phn tch nhng nguyn nhn a n vic r r thng tin

Ni dung chnh: 1.1Vai tr quan trng ca thng tin trong mt n v.

Vy an ton thng tin l g?

Khng th m bo an ton 100%, nh ng ta c th gim bt cc ri ro khng mongmun d i tc ng t mi pha ca cc lnh vc hot ng kinh t x hi . Khi cc t chc,n v tin hnh nh gi nhng ri ro v cn nhc k nhng bin php i ph v ATTT, hlun lun i n kt lun: nhng gii php cng ngh (k thut) n l khng th cung cp s an ton. Nhng sn phm Anti-virus, Firewalls v cc cng c khc khng th cungcp s an ton cn thit cho hu ht cc t chc. ATTT l mt mt xch lin kt hai yu t:yu t cng ngh v yu t con ng i.

1. Yu t cng ngh: bao gm nhng sn phm nh Firewall, phn mm phng chng virus,gii php mt m, sn phm mng, h iu hnh v nhng ng dng nh : trnh duytInternet v phn mm nhn Email t my trm.

2. Yu t con ng i: L nhng ng i s dng my tnh, nhng ng i lm vic vi thng tinv s dng my tnh trong cng vic ca mnh.

Hai yu t trn c lin kt li thng qua cc chnh sch v ATTT.

Theo ISO 17799, An Ton Thng Tin l kh nng bo v i vi mi tr ng thng tin kinh tx hi, m bo cho vic hnh thnh, s dng v pht trin v li ch ca mi cng dn, mit chc v ca quc gia. Thng qua cc chnh sch v ATTT , lnh o th hin ch vnng lc ca mnh trong vic qun l h thng thng tin. ATTT c xy dng trn nn tngmt h thng cc chnh sch, quy tc, quy trnh v cc gii php k thut nhm mc chm bo an ton ti nguyn thng tin m t chc s hu cng nh cc ti nguyn thngtin ca cc i tc, cc khch hng trong mt mi tr ng thng tin ton cu. Nh vy , vi vtr quan trng ca mnh , c th khng nh vn ATTT phi bt u t cc chnh schtrong con ng i l mt xch quan trng nht.


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Con ng i khu yu nht trong ton b qu trnh m bo an ton thng tin . Hu nhphn ln cc ph ng thc tn cng c hacker s dng l khai thc cc im yu ca hthng thng tin v a phn cc im yu rt tic li do con ng i to ra. Vic nhn thckm v khng tun th cc chnh sch v ATTT l nguyn nhn chnh gy ra tnh trng trn. n c l vn s dng mt khu c quy nh rt r trong cc chnh sch v ATTTsong vic tun th cc quy nh li khng c thc hin cht ch. Vic t mt mt khukm cht l ng, khng thay i mt khu nh k, qun l mt khu lng lo l nhng khu

Ph ng php nh gi cht l ng h thng ATTT

C l khng mt v lnh o no dm khng nh ni b cng ty l thc s an ton v tincy. Trong bi cnh nn kinh t th tr ng nh hin nay, s canh tranh din ra gay gt thmch gia cc nhn vin trong ni b cng ty: tranh dnh khch hng , mc ch thng tinhoc cc mc ch khng lnh mnh khc. mt s t chc, li dng s lng lo trongqun l v ATTT, nhn vin c nhng hnh vi bt l ng nh ly cp thng tin mt, chimot ti khon khch hng , n cp tin thng qua h thng tn dng Theo thng k,khong 70% cc ri ro v ATTT l xut pht t ni b trong t chc. Mt trong nhng cuhi lun c t ra tr c cc nh lnh o v cc nh qun tr thng tin l: H thng thngtin ca t chc an ton n mc no? Cu hi ny l mi quan tm ln nht v cng lvn nhy cm nht trong cc khu qun l h thng thng tin.

Tr li cu hi ny tht khng n gin nh ng khng phi l khng c cu tr li. giip vn trn, ch yu da vo hai ph ng php nh gi ATTT nh sau:

+ Ph ng php nh gi theo cht l ng ATTT ca h thng bng cch cho im.V d: hthng t 60/100 im hoc 60%

+ Ph ng php nh gi theo s l ng thit b - cng ngh bo mt.

Trong thc t , ph ng php nh gi theo cht l ng l ph ng php duy nht nhgi mc an ton ca cc ti nguyn trong h thng thng tin. Vit Nam, vic nh gi ATTT theo cht l ng l hon ton mi. Ng i ta d ng nhn vic trang b mt cng c ATTT nh (Firewall, Anti-virus) l m bo c ATTT cho h thng. Cht l ng ATTTphi c nh gi trn ton b cc yu t m bo tnh an ton cho h thng t t chc,con ng i, an ninh vt l, qun l ti nguyn n vic s dng cc cng c k thut. Nicch khc, cht l ng ATTT c nh gi trn c s thc thi cc chnh sch v ATTTtrong h thng. Cc chnh sch ny c chun ho v c cng nhn l cc tiu chunv ATTT p dng trn phm vi ton th gii.

Ph ng php nh gi theo s l ng khng c s dng.

Tiu chun nh gi v cht l ng ATTT.

Vic nh gi mc ATTT ca cc t chc th ng c tin hnh theo kinh nghim vda trn cc quy nh mang tnh cm tnh , cc b ca t chc m khng tnh n cctiu chun c th gii cng nhn . Vi nm tr c y, Vin Tiu chun ca Anh (BSI)cng vi mt s t chc th ng mi khc nh Shell, National Westminster Bank, MidlandBank nghin cu v xut mt tiu chun v ATTT. n nm 1995, tiu chun ny c cng nhn l tiu chun quc gia v qun l ATTT - BS7799. Tiu chun ny c lpvi m hnh hot ng ca cc cng ty. Lnh o cng ty, cc CSO/CIO da trn cs cc tiu chun ny thit lp cc chnh sch ATTT cho n v mnh. Ngay sau khi r ai, BS7799 c s dng 27 n c bao gm cc n c thuc khi lin hip Anh cng


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nh mt s quc gia khc nh Thy S, H Lan... n nm 2000, T chc tiu chun thgii ISO trn c s BS7799 xy dng tiu chun ISO 17799 v tiu chun ny tr thnhtiu chun quc t v qun l cht l ng ATTT (ISO/IEC 17799). Tnh n thng 2/2005 c khong hn 1000 t chc nhn chng ch ISO 17799 trong c Hitachi, Nokia,

Nhng phn c bn ca ISO 17799:

1. Chnh sch chung2. An ninh nhn s (Personel Security)3. Xc nh, phn cp v qun l ti nguyn (Asset Identification, Classification & Control). 4. An ninh vt l (Physical Security).5. An ninh t chc (Security Organization).6. Qun tr IT v mng (IT operations and network management).7. Qun l truy cp v cc ph ng php (Access control & methods).8. Pht trin HT v bo tr (System development & maintenance).9. Tnh lin tc trong kinh doanh v k hoch phc hi sau s c (Bussiness Continuty &Disaster Recovery Planning)10. Ph hp h thng vi cc yu t v lut php, o c (Low, Inestigation and Ethics).

Hnh 1.1 Nhng phn c bn ca ISO 17799

Chnh sch v an ton thng tin c t chc theo m hnh kim t thp.Cch t chc nygip cho cc nh lnh o qun l cht l ng an ton thng tin mt cch khoa hc v hiuqu.

Trn nh kim t thp m t cc chnh sch c p dng trong t chc .Ti sao ta phi thit lp chnh sch ny ? Phm vi v i t ng tc ng ca chnh sch? . Khng c mtchnh sch p dng chung cho mi n v. Trong mt t chc c nhiu b phn , tng bphn li c chc nng nhim v khc nhau, tnh cht v cch t chc thng tin cng khcnhau .B phn kinh doanh c m hnh thit k h thng ring vi c s d liu mang cth kinh doanh , b phn sn xut ,b phn nghin cu cng c cu trc h thng v c sd liu ca ring mnh .Trnh nhn thc v an ton thng tin cng rt chnh lch . Chnhv vy khi thit lp cc chnh sch ,nh qun l cn xc nh r mc ch ca chnh sch c thit lp , i t ng thc thi , phm vi tc ng

Lp th hai trn m hnh m t cc quy tc ,quy nh thc thi cc chnh sch . thc hin cc chnh sch ta phi lm g ? H thng cc quy tc ATTT c th hin trn 10 lnh vcln bao hm cc quy nh t t chc , con ng i , an ninh vt l n cc cng c k thut anton thng tin .Cc quy tc c xy dng trn m hnh IT chun ca t chc v th hin


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c tnh c th ca t chc .Thng qua vic thc thi cc quy tc , c th nh gi chtl ng an ton thng tin ca mt t chc thng qua kim ton (Audit) .

Lp th ba l lp cui cng ca m hnh . y l cc quy trnh , cc gii php h tr thc thicc quy tc , quy nh trn.N tr li cho cu hi lm nh th no thc thi cc quy nhtrn ? Cc nh qun tr an ton thng tin (CSO) cng cc qun tr IT thit lp cc quy trnhny v ph bin n mi nhn vin trong t chc ,v d Quy trnh thay i mt khu,Quytrnh ci t cc ch ng trnh dit virut ,chng cc ch ng trnh c hi v.v.Cc quy trnhny c th lin quan n nhiu chnh sch v i t ng s dng khc nhau.

Vic p dng ISO 17799 em li li ch g cho t chc?

Vic p dng cc tiu chun v ATTT theo ISO 17799 lm tng nhn thc cho i ng cnb nhn vin v ATTT. Xy dng mt mi tr ng an ton, c kh nng min dch tr c ccri ro, gim thiu cc nguy c do con ng i gy ra. Tiu chun ISO 17799 ra nhngnguyn tc chung trong qu trnh thit k , xy dng h thng thng tin mt cch khoa hc,gip cho vic qun l h thng tr nn sng sa, an ton, minh bch hn. Chng ta xydng mt bc t ng ng i an ton (Secure People Wall) trong t chc. Mt mi tr ngthng tin an ton, trong sch s c tc ng khng nh n vic gim thiu chi ph vt chtu t cho ATTT vn d rt tn km. V lu di, vic nhn c chng ch ISO 17799 l mtli khng nh thuyt phc vi cc i tc, cc khch hng v mt mi tr ng thng tin anton v trong sch . To iu kin thun li cho s hi nhp mt mi tr ng thng tin lnh

1.1 Vn o to ngun nhn lc

Theo IDG vo khong nm 2006 s bng n mt ngh mi trong lnh vc IT ngh an tonthng tin.Chc danh CSO (Chief Security Officer) tr nn quen thuc trong lnh vc IT.

Cp nht v nng cao kin thc v ATTT v nhn thc v vai tr ca n trong h thng IT lmt iu rt quan trng v cp bch v xt cho cng hnh ng ca con ng i l yu tquyt nh . Mc d ATTT c bit n rng ri nh ng yu t con ng i th ng t ccc t chc quan tm n. i vi nhng nh qun tr, h cn mt chnh sch an ton vmt ch ng trnh nhn thc cng nh nh gi cht l ng v ATTT nh ng tic rng hinnay ch a c nhiu gii php thc s quan tm vo vn lm sao tng c ng s vngchc cho mi lin kt vn d rt yu t ny trong mt xch ATTT

Hin nay, mt s doanh nghip ti Vit Nam c s chuyn bin tch cc trong vn nhn thc v ATTT. H sn sng u t ngn sch o to ngun nhn lc nhm to nntng vng chc v nhn thc v kin thc ATTT cho i ng nhn vin ca doanh nghip. in hnh l nh : S Khoa hc v Cng ngh ng Nai, Cng ty Bo him Bo Minh,Fujitsu Vietnam, Ngn hng Chu ...

Bn cnh vn cn nhiu doanh nghip nht l cc doanh nghip va v nh vn ch atip cn v hiu ht tm quan trng ca vic thit lp cc chnh sch v ATTT v qun l tiuchun cht l ng ATTT theo ISO 17799 thc s vn cn xa l v mi m i vi h. 1.2 Phn tch nhng nguyn nhn a n thng tin trn a b mt


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-RAID controller b hng.( Redundant Array of Independent Disks) -Ng i dng v hoc khng l u thay a mi khi a b h ,gy ra s h hng ca a khc trong cng mt RAID. -D liu RAID registry trong b nh b hng. -Tng v tt in p t ngt, thm ha t nhin. -Li do ng i s dng, v tnh xa thng tin hoc li phn mm ca a cng. -Ng i s dng reconfigure dung l ng a cng sai. -Virus tn cng hoc ng i s dng v tnh nh dng sai mt a cng trong h thngRAID.RAID l ch vit tt ca Redundant Array of Independent Disks. Ban u, RAID c sdng nh mt gii php phng h v n cho php ghi d liu ln nhiu a cng cng lc. Vsau , RAID c nhiu bin th cho php khng ch m bo an ton d liu m cn gipgia tng ng k tc truy xut d liu t a cng. Tuy nhin vic mt d liu t RAIDkhng phi l chuyn khng c, v ng i s dng th ng cm thy ch quan v RAID n nthiu s sao l u d liu cn thit.Cc loi RAID: RAID 0:Cn c gi l "Striped Volume", n c s dng gia tng s truy cp d liu. Trongcu hnh RAID 0 ny n c th h tr t 2 disks cho n 32 physical disks, d liu c chiau ra trn cc disks, v n lm vic nh l mt logical khi (Volume). Mc d n c gil RAID (Redundancy Array of Inexpesive Disk), nh ng tht s trong cu hnh ny n khngc "Redundancy". Vi cu hnh RAID ny, nu mt trong hai disk ca khi RAID ny rt th s truy cp d liu vo khi ny s b mt ht. RAID 1:Cu hnh RAID ny cn c gi l cu hnh "Khi Phn Chiu" (Mirrored Volume), trongcu hnh ny d liu c mirrored gia hai physical disks cho mc ch redundancy. ViRAID 1 tt c nhng d liu c vit v volume th nht trong khi mirrored th n s c vit v volume th hai trong khi ny bi fault tolerant driver ftdisk.sys. D liu v vy

c m bo an ton hn Raid 0. RAID 1+0:L s kt hp ca Raid 0 v Raid 1 vi s hin din ca Fault Tolerance a ra mt hthng hon ho c u im ca c hai loi Raid,s nhanh nhy ca Raid 0 v s an tonca Raid 1.Tuy nhin chi ph cho mt h thng ny kh t v phi cn t nht 4 a cng c th thit lp. RAID 5:RAID 5 th ng c bit nh l "Stripe set with parity". Trong cu hnh RAID ny, n sdng t nht l 3 v nhiu nht l 32 physical disks, khng ch ring d liu c phn phiu trn cc disk m nhng thng tin lin kt cng c phn phi trn cc disks, chcchn rng d liu s c cu thnh li nu mt trong nhng disk c lp b rt. Ni nghn l nu bt k disk no trong khi ny b rt th bn c th thay i mt disk mi v n st ng cu hnh li (Rebuild) tt c nhng d liu b mt.Cc loi RAID khc:Ngoi cc loi c cp trn, bn cn c th bt gp nhiu loi RAID khc nh ngchng khng c s dng rng ri m ch gii hn trong cc h thng my tnh phc vmc ch ring, c th k nh : Level 2 (Error -Correcting Coding), Level 3 (Bit-InterleavedParity), Level 4 (Dedicated Parity Drive), Level 6 (Independent Data Disks with DoubleParity), Level 10 (Stripe of Mirrors, ng c li vi RAID 0+1), Level 7 (th ng hiu ca tpon Storage Computer, cho php thm b m cho RAID 3 v 4), RAID S (pht minh catp on EMC v c s dng trong cc h thng l u tr Symmetrix ca h). Bn cnh cn mt s bin th khc, v d nh Intel Matrix Storage cho php chy kiu RAID 0+1 vich 2 cng hoc RAID 1.5 ca DFI trn cc h BMC 865, 875. Chng tuy c nhiu im

khc bit nh ng a phn u l bn ci tin ca cc ph ng thc RAID truyn thng. 1.3Phn tch nhng nguyn nhn a n r r thng tin trn my tnh


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R r thng tin trong doanh nghip qua th nh: Thng th ng, mi ng i c th dng nhng thit b kiu ny t do trong gi lm vic mkhng cn s cho php ca cp trn. Th nh c nhn vin mang i kh p phng v cmvo cng USB sao chp bi ht c s n trong my tnh ca ng i khc.Tuy nhin, s lng lo ny s tip tay cho bt c ai cng c th l u ton b thng tin trn

my tnh no vo trong th nh dung l ng ln mt cch c ch ht sc nhanh chng.R rng, trong khi nhiu hng tiu tn c ni tin bo v mnh thot khi nguy c t virus, spyware, spam. .., th h li qun li cnh bo mun thu ca cc chuyn gia b o mtr ng him ha ln nht bao gi cng nm chnh bn trong mi cng ty.Mt s hng thc hin nhiu bin php ngn cn vic sao chp d liu t my tnhvo th nh v my nghe nhc, nh ng c m dng nhng thit b ny l v l v s khng th thc hin c trn thc t. Do , cc cng ty cn trang b nhng cng c, ng dng tinhvi c th ghi li hot ng ca ng i trong mng ni b trnh tht thot d liu, r r thng tin hoc nhim virusR r thng tin trong doanh nghip qua my tnh xch tay: Trong nhiu tr ng hp, nhn vin mang thng tin ca cng ty ra khi vn phng bngchic laptop. Tuy nhin, h khng bo v s an ton cho chng v t ra ngi ngn khi dng

cc c ch m ha nh ci password cho my v cc tp tin. Alan Paller, Gim c Hcvin SANS chuyn nghin cu vn bo mt my tnh, gii thch l do l nu h qun mtkhu th s khng m c tp tin v cc thao tc ny c v lm chm cng vic ca h. iu ny khin cc nh sn xut my tnh l u tm v bt u tch hp c ch m havo sn phm. V d nh h iu hnh Windows Vistaca Microsoft s gip ng i s dngd dng m ha d liu ca mnh hn. Cc cng ty c l ng ln nhn vin di ng cng bt u quan tm n iu ny. V d nhhng t vn ti chnh Ernst & Young vi 30.000 my tnh xch tay phc v cho cng ty angm ha tt c ni dung trn my sau v thng tin v 243.000 khch hng ca h cha trongmt chic laptop b nh cp, bao gm tn, a ch, thng tin th tn dng. 1.4Mt s bin php khc phc.

Cc chuyn gia a ra li khuyn vi cc bc sau :1. Phi kim sot d liu Chc chn bn khng th no kim sot c thng tin nhy cm hay thng tin bn quyntrn mng nu ngay c v tr ca chng nm u bn cng khng bit.D liu nhy cm ca mt t chc th ng c phn phi rng ri qua mng ni b. Dliu quan trng th ng khng ch nm trong c s d liu (CSDL) m c khi c trong thin t, my tnh c nhn v i khi ng vai tr nh kiu i t ng d liu trong cng Web.Thng tin nhy cm cng c nhiu kiu khc nhau, nh m s th tn dng, m s bo mtx hi (CMT, th sinh vin). Cc b mt th ng mi c th c tm thy trong nhiu loi

file, vn bn khc nhau theo kiu thng tin lin h khch hng, hp ng, chi tit k thutpht trin sn phm.Trin khai quy nh kim sot cho tt c cc loi d liu th ng khng mang li hiu qu vkhng thc t. Thay vo , hy phn loi tng lp d liu v chn ra quy nh kim sotph hp nht cho mi loi. Bn cng c th s dng mt s cng c r sot mng t ngv xc nh v tr d liu nhy cm. Nhiu hng cung cp cc loi cng c ny nhReconnex, Tablus, Websense. S l ng sn phm ca cc hng ngy cng phong ph.Nhiu trong s c th phn tch d liu thnh nhiu loi khc nhau, da trn quy nh docng ty t ra.

2. Gim st ni dung di ng Khi cc cng ty s dng Website trong giao dch th ng mi v lin kt vi nhiu mng
http://vnexpress.net/Topic/?ID=2698http://vnexpress.net/Topic/?ID=2523http://vnexpress.net/Search/?p=1&r=89&a=1&s=Windows%20Vistahttp://vnexpress.net/Search/?p=1&r=89&a=1&s=Windows%20Vistahttp://vnexpress.net/Search/?p=1&r=89&a=1&s=Windows%20Vistahttp://vnexpress.net/Topic/?ID=2523http://vnexpress.net/Topic/?ID=2698


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thuc v i tc, nh cung cp hay khch hng th vn sng cn l phi theo di c cig ang din ra, ang tri ni qua cc mng. Gim st ni dung l phn c s ct li trongchin l c bo v d liu ca nhiu cng ty. Vi qu nhiu im ra mng cho d liu, iuquan trng nht l phi gim st c l u l ng mng.

Tt c cc hng sn xut nh Ver icept Corp., Vontu Inc., Oakley Networks Inc., Reconnexv Websense u bn mt lot sn phm c chc nng kim tra, r sot e -mail, trnh tinnhn tc thi (Instant Messaging), h thng chia s file peer -to-peer, qu trnh post Web vc cc website FTP nhm pht hin v tm kim hot ng xm phm d liu hay vi phmquy tc t ra trong cng ty. Cc cng c ny c t gn cng vo mng v c thit k a ra cnh bo khi pht hin gi d liu ng ng. Nhiu sn phm c th c dng thc p cc hot ng nh loi b hay m ho d liu khi d liu c truyn ra ngoi.V d, mt trong s l cc cng c lc ni dung, cho php bn thy c tt c nhng gang n hoc ang ra ngoi mng. Nh Bowers ca cng ty hng u Wyeth nhn xt:Chng ti gim st c tt c cc cng v tt c giao thc truyn ti ni dung khi hngny trin khai cng c lc ni dung.3. Hy mt n c s d liu c cha nhng thng tin qu bu ca cng ty ng dng li vic bit ai ang truy cp c s d liu. Bn cn cn phi phi bit khi no, u, nh th no v ti sao h li thc hin truy cp ny. Nhiu cng c h tr c xydng, cho php cc cng ty gim st truy cp hay cc hot ng trn c s d liu. Bn cth dng sn phm ca Imperva Inc., Guardium Inc., Application Security Inc. v LumigentTechnologies Inc. Chng c thit k nhm mc ch gip bn bit ng i dng hay adminno ang lm vic trn c s d liu vi c quyn truy cp, hay chnh sa, copy, xo,download s l ng ln tp hp cc file, hoc a ra cc cnh bo khi ai c gng thchin mt trong cc hot ng trn. Cc sn phm ny cng cung cp du vt kim tra kh rrng theo di khi c ng i vi phm quy nh ca doanh nghip.M ho d liu nhy cm trong c s d liu l mt ph ng php khc ng xem xt.4. Gii hn c quyn ng i dng Hu ht cc cng ty u cung cp nhiu c quyn cho ng i dng hn so vi cn thit. l nhn nh ca Amichai Shulman, gim c cng ngh ca Imperva. Gim st truy cp dliu cc k quan trng ca ng i dng v theo di truy cp khng xc nh vi d liu mc nguy him cao l nhng b c khng th thiu.To quy nh truy cp nhm gii hn c quyn mng ca ng i dng mt cch cht ch.Ch cho php truy cp lp d liu t ng ng cn thit cho cng vic ca tng kiu ng idng, ng thi thit lp cc iu khin nhm bt buc nhn vin trong cng ty phi tun thquy nh ni b xy dng. V d, a ra cnh bo khi ai vn bnh th ng ch lm vicvi 10 tp ti liu mi ngy, t nhin bt u truy cp s vi l ng ln hn.Vic a ra quyt nh iu khin truy cp cho thnh vin ni b v ng i ngoi l kh ngin, Matt Kesner- gim c cng ngh ca Fenwick & West LLC, hng lut c tr s tiCalifoocnia (M) khng nh. Nh ng i khi ng i bn ngoi li cn truy cp hp php dliu ca doanh nghip vi s l ng ngang bng hoc thm ch ln hn nhu cu ca nhnvin ni b. V d, cc mng Extranet client ca Fenwick & West ang c s dng th ngxuyn bi khch hng hp tc vi nhn vin u quyn ca hng. i khi, ng i dng bn


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ngoi hng th vi d liu ca doanh nghip hn nhiu so vi ng i trong ni b cng ty.5. Quan tm ti cc im cui S pht trin nhanh chng ca th tr ng thit b di ng nh lapto p, cc my xch tay khc,th nh USB hay my nghe nhc iPod ngy cng to iu kin cho nhng k c xu

trong ni b cng ty n cp d liu d dng hn. Cc cng ty cn phi pht trin hot ngiu khin v gim st tp trung ho. Trong , thit b phi c gn vo mng v h thngdoanh nghip, quy nh r d liu no c download, upload hay l u tr ti u. Thc hin c cc cng vic ny l c mt thch thc. Nh ng bn khng cn qu lo lng, v mt ssn phm ca cc hng nh Code Green Net works Inc., ControlGuard Inc. v SecureWaveSA s gip bn d dng hn khi tin hnh cc hot ng mong mun.Trc y, c rt t cng ty t cc kim sot hiu qu vo ng ni cn thit cho phph gim st h thng ni b mt cch cht ch v theo di c qu trnh di chuyn haytruyn vn ca d liu, Alex Bakman- gim c iu hnh ca Ecora Software Corp khngnh. iu c ngha l hot ng ph hoi tng din ra khng kn khng trng trongsut thi gian di.6. Tp trung ho d liu bn quyn tr tu i vi mt cng ty ln, vic bo v bn quyn tr tu ri rc trn nhiu h thng l iukhng th. Do , l u tr cc d liu ny trong mt h thng th vin ti nguyn tp trungho bt c khi no c th l bin php an ton v tin li trong trong bo mt cng nh chias thng tin.Thng thng, ngi ta t tt c trng vo trong mt r, Ira Winkler- chuyn vin t vnbo mt t do v ph trch chuyn mcComputerworld.com v von. Nhng trong trnghp ny, bo v mt h thng s d dng hn l bo v v s h thng con nm ri rc can .

Cu hi v bi tp: 1. Trnh by cc ph ng php nh gi cht l ng h thng ATTT.

2. Phn tch nhng nguyn nhn a n thng tin trn a b mt ? Nu cc bin php khc phc.

3. Phn tch nhng nguyn nhn a n r r thng tin trn my tnh? Trnh by cc bin php khcphc.


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BI 2

Tn bi : L U TR H THNG THNG TIN TRN CC THIT B L U TR M bi : ITPRG03-19.2

Gii thiu : L u tr d liu an ton v khoa hc l vic rt quan trng trong lnh vc cngngh thng tin. Bi hc cung cp cc kin thc c s v hnh thc, cch thc v thit b l utr, phc hi bo v h thng d liu.

Mc tiu thc hin: - S dng c cc thit b l u tr thng dng - Sao l u d liu d i nhiu hnh thc .- Phc hi d liu trong mt s tr ng hp - S dng c mt s phn mm tin ch v phn mm cng c phc hi, bo v choh thng thng tin.

Ni dung chnh: I. Cu trc ca th mc v tp tin trn my n v trn h thng mng

my tnh.1. T chc a

T chc a l mt trong nhng c tr ng c bn ca h iu hnh. a mi muahoc a s dng vi mt iu hnh khc khng t ng thch vi h iu hnh ang s

dng th khng th dng c. Lc ny ta phi tin hnh t chc a cho c cu trc m hiu hnh hin ang dng hiu c.

T chc a cho php qun l c cc d liu c ghi trn a nh cc tp tin,qun l vng nh, c/ghi thng tin,...

Vic t chc a th ng c tin hnh bng ch ng trnh nh dng a: FORMAT.Khi gi ch ng trnh ny bng lnh FORMAT ch ng trnh s t ng thi hnh cc b ccn thit t chc a (nh dng a).

Ch ng trnh ny t chc a nh sau : - To ra cc rnh (track) trn b mt a, chia s sector trn 1 rnh, nh s Byte trn

mi sector. - Sao chp to tp tin mi (boot record) - To bng cp pht a cho tp tin: bng FAT - To th mc gc (root directory) - Xc nh vng ghi tn, vng l u tr d liu.

a tr c khi s dng phi c nh dng (format) mi c th l u tr d liu ln c.

Mi h iu hnh c cch t chc a ring. HH Windows 98 t chc cu trc atheo dng FAT (file allocation table).

Khi nh dng a, HH s chia mi mt a ra thnh nhng ng trn ng tm(track) c nh s t ngoi vo trong v bt u t 0.


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Mi track c chia thnh nhiu on nh gi l cung t (sector), cc cung t cnh s bt u t 1. Mi cung t th ng cha 512 bytes. D liu s c l u trn tngcung t.

Hnh 1 .2: cch phn chia mi mt a khi c nh dng. 2. Th mc v tp tin 2.1 Tp tin:

a) Tp tin (file) :Tp tin l hnh thc, n v l u tr thng tin trn a ca h iu hnh.Ni dung ca tp tin l thng tin cn l u tr. Tp tin (vit tt cho tp thng tin; cn c gi l tp, tp tin, file) l mt tp hp ca thng tin c t tn. Thng th ngth cc tp tin ny cha trong cc thit b l u tr nh a cng, a mm, CD, DVDcng nh l cc loi chip in t dng k thut flash c th thy trong cc nh cgiao din USB. Ni cch khc, tp tin l mt dy cc bit c tn v c cha trong ccthit b l u tr d liu k thut s.

b) c im Mt tp tin lun lun kt thc bng 1 k t c bit (hay du kt thc) c m

ASCII l 255 h thp phn. K t ny th ng c k hiu l EOF ( End OfFile ).

Mt tp tin c th khng cha mt thng tin no ngoi tr tn v du kt thc.Tuy nhin, iu ny khng h mu thun vi nh ngha v bn thn tn ca tptin cng cha thng tin. Nhng tp tin ny gi ltp tin rng hay tp tintrng .

di (kch th c) ca tp tin c th ch ph thuc vo kh nng ca my tnh, kh nng ca h iu hnh cng nh vo phn mm ng dng dng n. n vnh nht dng o di ca tp tin l byte. di ca tp tin khng bao gm di ca tn tp tin v du kt thc.

c) Thuc tnh Nhng c tnh v gii hn ca tp tin gi lthuc tnh ca tp tin. Cc loi thuc tnh Ty theo h thng tp tin m cc thuc tnh ny c th khc nhau. Th d cc thuc tnh trn h thng tp tin FAT bao gm:

Archive: l u tr. Trn cc h iu hnh DOS th thuc tnh ny c nh khi mikhi tp tin b thay i, v b xa khi thc hin lnh backup sao l u d liu .

Hidden: n. Khi mt tp tin c thuc tnh ny th cc ch ng trnh lit k cc tp tintheo mc nh s b qua, khng lit k tp tin ny. Ng i s dng vn c th lm

vic trn tp tin ny nh bnh th ng. Read-only: ch c. Khi mt tp tin c thuc tnh ny th cc ch ng trnh x l tptin theo mc nh s khng cho php xa, di chuyn tp tin hoc thay i ni dung

Track

Sector
http://vi.wikipedia.org/wiki/%C4%90%C4%A9a_c%E1%BB%A9nghttp://vi.wikipedia.org/wiki/%C4%90%C4%A9a_c%E1%BB%A9nghttp://vi.wikipedia.org/w/index.php?title=%C4%90%C4%A9a_m%E1%BB%81m&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90%C4%A9a_m%E1%BB%81m&action=edithttp://vi.wikipedia.org/wiki/CDhttp://vi.wikipedia.org/wiki/DVDhttp://vi.wikipedia.org/wiki/Flashhttp://vi.wikipedia.org/wiki/Flashhttp://vi.wikipedia.org/w/index.php?title=Giao_di%E1%BB%87n&action=edithttp://vi.wikipedia.org/w/index.php?title=Giao_di%E1%BB%87n&action=edithttp://vi.wikipedia.org/wiki/Bithttp://vi.wikipedia.org/wiki/Bithttp://vi.wikipedia.org/wiki/K%E1%BB%B9_thu%E1%BA%ADt_s%E1%BB%91http://vi.wikipedia.org/wiki/K%E1%BB%B9_thu%E1%BA%ADt_s%E1%BB%91http://vi.wikipedia.org/wiki/ASCIIhttp://vi.wikipedia.org/wiki/H%E1%BB%87_th%E1%BA%ADp_ph%C3%A2nhttp://vi.wikipedia.org/wiki/M%C3%A1y_t%C3%ADnhhttp://vi.wikipedia.org/wiki/M%C3%A1y_t%C3%ADnhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/Ph%E1%BA%A7n_m%E1%BB%81m_%E1%BB%A9ng_d%E1%BB%A5nghttp://vi.wikipedia.org/wiki/Ph%E1%BA%A7n_m%E1%BB%81m_%E1%BB%A9ng_d%E1%BB%A5nghttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=DOS&action=edithttp://vi.wikipedia.org/w/index.php?title=Sao_l%C6%B0u_d%E1%BB%AF_li%E1%BB%87u&action=edithttp://vi.wikipedia.org/w/index.php?title=Sao_l%C6%B0u_d%E1%BB%AF_li%E1%BB%87u&action=edithttp://vi.wikipedia.org/w/index.php?title=Sao_l%C6%B0u_d%E1%BB%AF_li%E1%BB%87u&action=edithttp://vi.wikipedia.org/w/index.php?title=DOS&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Ph%E1%BA%A7n_m%E1%BB%81m_%E1%BB%A9ng_d%E1%BB%A5nghttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/M%C3%A1y_t%C3%ADnhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_th%E1%BA%ADp_ph%C3%A2nhttp://vi.wikipedia.org/wiki/ASCIIhttp://vi.wikipedia.org/wiki/K%E1%BB%B9_thu%E1%BA%ADt_s%E1%BB%91http://vi.wikipedia.org/wiki/Bithttp://vi.wikipedia.org/w/index.php?title=Giao_di%E1%BB%87n&action=edithttp://vi.wikipedia.org/wiki/Flashhttp://vi.wikipedia.org/wiki/DVDhttp://vi.wikipedia.org/wiki/CDhttp://vi.wikipedia.org/w/index.php?title=%C4%90%C4%A9a_m%E1%BB%81m&action=edithttp://vi.wikipedia.org/wiki/%C4%90%C4%A9a_c%E1%BB%A9ng


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tp tin. Cn cc thao tc khc nh i tn tp tin, c ni dung tp tin vn c chophp.

System : thuc v h thng. Mt tp tin c thuc tnh ny s chu cc hn ch baogm cc hn ch ca thuc tnhHidden v cc hn ch ca thuc tnh Read-only ,ngha l khng b lit k, khng th xa, di chuyn, thay i ni dung. Thuc tnh nych yu dng cho cc tp tin quan trng ca h iu hnh.

Sub-directory (hay directory ): th mc con. Nhng tp tin c thuc tnh ny cx l nh l th mc . Th mc l tp tin dng c bit, ni dung khng cha dliu thng th ng m cha cc tp tin v cc th m c khc.Ngoi ra, cn rt nhiu thuc tnh khc ca cc tp tin m ty theo h iu hnh s c nh ngha thm vo. Th d i vi h iu hnh Linuxcc tp tin c th c thm cc thuc tnh nh ccquyn s dng tp tin, c im ca tp tin, v thng tin v cc loi tp tin nh l ccloi tp tin lin kt mm, cc socket, cc pipe ...L u : Cc thuc tnh ca mt tp tin th ng khng nh h ng n ni dung thngtin ca tp tin nh ng li nh h ng rt nhiu n chc nng v vic x dng tptin. Th d cc tp tin khng c thuc tnh cho php thi hnh th khng th xem l mt

phn mm kh thi c mc d ni dung ca n c th ch cha cc ch th my tnh.Cch lm tp tin tr nn kh thi l thay i thuc tnh kh thi ca n hay l phithay i phn ui ca tn tp tin (nh l tr ng hp ca h iu hnh Windows -DOS)

d) nh dng Cu trc ca mt tp tin nh ngha cch thc m tp tin c cha, c thc thi, vth hin trn cc thit b (nh mn hnh hay my in) gi lnh dng ca tp tin. nh dngny c th n gin hay phc tp. nh dng ca tp tin ph thuc vo nhiu yu t trong quan trng nht bao gm:

H iu hnh khc nhau v kin trc my tnh khc nhau c th i hi cc nhdng cho tp tin mt cch khc nhau.Th d: Trn cng mt kin trc Intel, tp tin vn bn dng n gin nht to nnbi h iu hnh Linux cng c s khc nhau vi tp tin vn bn ca Windows(hay DOS). D nhin, cc tp tin vn bn ny li cng khng th c c trncc my dng h iu hnh Mac OS (chng khc nhau hon ton v mt kintrc my tnh) nu khng c cc tin ch c bit chuyn i nh dng.

Tp tin dng cho cc mc tiu khc nhau cng s c cc nh dng khc nhau.Ngoi s rng buc v nh dng ca h iu hnh, cc tp tin dng trong ccng dng hay cc phn mm khc nhau cng s khc nhau v s khc nhau n yty thuc vo kin trc ca cc ng dng x dng cc tp tin .Th d d hiu nht l nh dng ca mt tp tin vn bn phi khc vi nh dngca mt tp tin hnh nh hay tp tin m thanh.

Cc tp tin dng cho cng mt mc tiu cng c th c nh dng khc nhau tutheo nh sn xut no thit k ra n.Th d: Trong cc tp tin hnh v ha th cc tp tin kiuBitmap (cc tp hnhc ui l .bmp) c nh dng hon ton khc vi cc tp tin kiuTagged ImageFile Format (ui ca lai tp tin ny l .tif) v cng khc vi tp tin kiuJointPhotographic Experts Group (vi cc ui c dng .jpg hay .jpeg).

e) Tn Ty theo h iu hnh m c th c cc qui c v tn tp tin. di ca tn tp tin ty thuc vo h thng tp tin. Ty thuc vo h thng tp tin v h iu hnh m s c mt s k t khng

c dng cho tn tp tin.Th d: Trn h iu hnh Microsoft Windows, khng c dng cc k t sau trong

tn tp tin: \ / : * ? " < > |Theo truyn thng c ca h thng DOS v Windows, tn tp tin th ng bao gm hai

phn: phn tn v phn m rng (cn gi l phn ui). Tuy nhin, tn ca mttp tin khng nht thit phi c phn m rng ny.
http://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edithttp://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edithttp://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edithttp://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edithttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/Linuxhttp://vi.wikipedia.org/wiki/Linuxhttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/wiki/Microsoft_Windowshttp://vi.wikipedia.org/wiki/Microsoft_Windowshttp://vi.wikipedia.org/wiki/Microsoft_Windowshttp://vi.wikipedia.org/wiki/Microsoft_Windowshttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/w/index.php?title=H%E1%BB%87_th%E1%BB%91ng_t%E1%BA%ADp_tin&action=edithttp://vi.wikipedia.org/wiki/Linuxhttp://vi.wikipedia.org/wiki/H%E1%BB%87_%C4%91i%E1%BB%81u_h%C3%A0nhhttp://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edithttp://vi.wikipedia.org/w/index.php?title=Th%C6%B0_m%E1%BB%A5c&action=edit


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Th d v cu trc bit ca tp tin ASCII

Hnh 1.3 : cu trc bit ca tp tin ASCII

Trong hnh trn l hai tp tin vn bn dng n gin dng m ASCII. Tp tin "hoso.txt" l tptin son ra bng lnh edit ca h iu hnh Windows. Tp tin th nh, "hoso2.txt", li cson tho bng lnh vi trong h iu hnh Linux. Hy l u qui c xung hng ca tp tintrong Windows s bao gm hai byte: du CR (cariage return ) c gi tr ASCII l 0x0D v duLF (line feed ) c gi tr 0x0A; trong khi , Linux ch cn du LF l . iu ny cho thy skhc nhau v nh dng.

2.2 Th mc Th mc (Directory, FOLDER) : Khi s l ng tp tin trn a nhiu n hng trm, hng ngn tp tin th vic tm li mt haymt nhm cc tp tin no s kh khn. d dng tm kim, cn to cc th mc cha cc tp tin cng ch , chc nng vo trong mt th mc.Th mc l hnh thc, n v qun l tp tin ca h iu hnh. Ni dung ca th mc l cctp tin m n qun l.

Cc th mc trn a c t chc theo dng phn cp, cc th mc xut pht t mt thmc chnh trn a gi l th mc gc (root directory). V cch t chc th mc trn aging nh mt ci cy nn s th mc trn a gi l cy th mc (directory tree).Th mc gc c k hiu \ do ch ng trnh nh dng a to ra. Cc th mc c totrong qu trnh lm vic gi l cc th mc con (subdirectory). Trn a khng c sn cy th mc ca n. Khi nh dng a h iu hnh to ra th mcgc. Sau ng i s dng s to ra cc th mc con khi cn. Mt s th mc c ccch ng trnh to ra trong lc ci t. Cc tp tin nn c t trong th mc con, ng tngay vo th mc gc. Mt khi s l ng tp tin c l u tr trn b nh ngoi ln ti 1 con s kh ln th nhtthit phi a ra khi nim th m c. Khi nim ny cng gn ging nh h thng th m ctrong th vin (khi mi tp tin c th v nh 1 cu n sch).Nu s sch khng l trong th vin khng c t chc theo mt tr t t hp l m c chung vo mt ch th khi mun tm 1 cun sch (theo 1 ch no m ta ch a bi t tnca cun sch chng hn), ta phi nhn vo tng cun mt, v khng phi th nhn tipqua cun khc cho n khi tm c. Cch lm c th khin ta phi mt 1 khong thigian r t kinh khng, nht l khi cun sch mun tm khng c trong th vin th ta vnphi xem ht tt c mi cun sch trong th vi n mi bit c l khng c! khc phctr ngi ng i ta t chc h thng th m c: danh mc tn sch c lit k theo tngch , trong mi ch li c th c nhiu ch con. Vic t chc phn cp dng cynh v y chc chn s gip cho thi gian tm kim 1 cun sch theo 1 ch no dch a bit tn sch cng s r t nhanh.Ni dung cc tp tin cn a dng hn ni dung ca cc quyn sch (khng ch l ti liu vnbn bnh th ng m cn c th l hnh nh, m thanh, nhc, phim, tr chi, ch ng trnhcc loi...), v s l ng tp tin trn b nh ngoi cng rt nhiu khin cho vic tm kim &s dng chng cng s r t kh khn nu nh ta cng chung vo 1 ch m khng t chc
http://vi.wikipedia.org/w/index.php?title=M%C3%A3_ASCII&action=edithttp://vi.wikipedia.org/w/index.php?title=M%C3%A3_ASCII&action=edithttp://vi.wikipedia.org/w/index.php?title=M%C3%A3_ASCII&action=edithttp://vi.wikipedia.org/wiki/Windowshttp://vi.wikipedia.org/wiki/Windowshttp://vi.wikipedia.org/wiki/Windowshttp://vi.wikipedia.org/wiki/Vihttp://vi.wikipedia.org/wiki/Vihttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Bytehttp://vi.wikipedia.org/wiki/Vihttp://vi.wikipedia.org/wiki/Windowshttp://vi.wikipedia.org/w/index.php?title=M%C3%A3_ASCII&action=edithttp://vi.wikipedia.org/wiki/H%C3%ACnh:Dinhdangtext.gif


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theo mt tr t t hp l. Do t chc h thng th m c phn cp trn b nh ngoi l r tcn thit, gii quyt nhu cu trn.Tm li, khi nim th mc cng c a ra b i h iu hnh, vic tm kim & s dngtp tin c hiu qu. Mi th mc c th cha cc tp tin v cc th mc con bn trong (dnhin trong mi th mc cng c th ch cha ton tp tin, hoc ch cha ton th m c con,hoc ang l th m c r ng khng cha g c).II. Cch l u tr d liu qua h thng bng FAT (FAT 16, FAT 32, FATNTFS...)T chc h thng tp tin trn a 1. Cc nh n xt & phn tch c n thit:

c th l u tr c thng tin /d liu vo a & truy xut, s dng c cc d liu trn a mt cch hiu qu th cn phi a ra nh ng phn tch, nhn xt sau:

i) Ph i xc nh cc v tr cn tr ng ( c th lu d li u vo a ) ii) M i sector(ho c t ng qut hn l mi block) ch thu c t i a 1 t p tin, t c n u sector ch ani dung c a 1 t p tin th trong sector s khng c n i dung c a t p tin khc( d qu n l, khng b nh m l n thng tin gi a 2 t p tin) iii) Tn & cc thu c tnhc a t p tin c n c lu ring vo 1 vng ( t c truy

xut d li u nhanh hn) iv) Phi c thng tin v tr b t u c a n i dung t p tin (do phn tch trn) v) N i dung t p tin khng b t bu c ph i lin t c (ph i cho php c lutr vo

cc vng khc nhau khi c n phn m nh) vi) Ph i bi t cc v tr ch a n i dungt p tin (do phn tch trn) vii) Ph i bi t cc v tr b h viii) Ni dung t p tin nn lu tr theo n v l CLUSTER (l dy N sector lin ti p

d qu n l & vi c truy xu t c nhanh hn)

2. Cluster2.1. K hi n i m

n v c ghi trn a l sector, nh ng n v l u tr ni dung tptin khng phi l mt sector m l mt cluster gm N sector lin tip

i v tr l u gi ni dung tp tin trong cc phn tch trn s tn ti trn vng d liu (vng DATA) nicha ni dung tp tin.

2.2. L d o pht s in h khi n i m Clusteri) Nu sector trn vng d liu qu nhiu th c th s kh hoc khng qun l c,

khi qun l trn cluster s d dng hiu qu hn.ii) Ni dung tp tin th ng chim nhiu sector v c th khng lin tc, v thi gian c

ghi mt ln n sector lin tip th ng nhanh hn nhi u so vi thi gian c ghi n lnm mi ln ch 1 sector. Do ti u th i gian truy xut tp tin th cn chn n v truy xut l mt khi nhiu sector.

2.3. Hnh th c t ch c a s c chia thnh 2 vng: vng d liu (DATA) cha ni dung tp tin v vng h

thng (SYSTEM) cha cc thng tin qun l. Vng SYSTEM c kch th c nh hn nhiuso vi vng DATA v phi truy xut mi khi s dng a nn th ng nm ngay u a,phn cn li thuc v vng DATA. Trn vng DATA l mt dy cc Cluster lin tip cnh ch s theo th t tng dn (bt u t 0, 1 hay 2 ty theo H iu Hnh). Nh vynu vng DATA cSD sector & bt u ti sector SS, mi Cluster chim SC sector, Clusteru tin c nh ch s l FC, th a s c tng cng SD/Sc Cluster v Cluster C s btu ti sector: SS + (C FC ) * SC

V d, nu a c kch th c 4014 sector, vng SYSTEM chim 11 sector, micluster chim 4 sector, Cluster u tin c nh ch s l 2; th phn b Cluster trn as nh sau:

Cluster 2 Cluster 3 Cluster 4 ... Cluster 1001... ...


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0 1 ... 10SYSTEM AREA

11 12 13 14 15 16 17 18 19 20 21 22 DATA AREA ... 4007 4008 40094010

Hnh 1.4 : phn b Cluster trn a

( 3 sector 4011, 4012, 4013 s khng thuc cluster no v khng c s dng)2.4. Kch th c Cluster

S sector trn 1 cluster nn l ly tha ca 2 v c gi tr ln hay nh l ty theo a.Nu ta chn kch th c cluster cng ln th s cng lng ph a v mt tp tin c kch th cnh vn phi dng mt cluster gm nhiu sector l u, nh ng khi s hn ch c s phn mnh ca tp tin v v vy tp tin c th an ton hn & truy xut nhanh hn. Kchth c ca Cluster ph thuc vo kh nhiu yu t: dung l ng a, tc truy xut 1 dysector trn a, kch th c ca a s tp tin s l u vo a, s cluster ti a m h thng cth qun l, nhu cu ca ng i s dng, Trn cc a cng hin ti th Cluster th ng ckch th c 4, 8 hoc 16 sector.V d:

-Vi a mm 1.44 MB bnh th ng (c 2880 sector), nu ta cho 1 cluster chim 1000sector th s r t khng hp l. V khi ta ch c th chp c ti a 2 tp tin voa, du mi tp ch c kch th c l 1byte! Tuy nhin nu ta ch ton chp vo acc tp tin c kch th c gn 1000 sector th s khng cn s lng ph na.

-Vi h thng ch c th qun l ti a M Cluster, nu vng DATA ca a c 100Msector th ta phi cho mi Cluster ti thiu 100 sector mi c th qun l c tonb vng DATA

3. Bng qu n l Cluster3.1. K hi n i m

L 1 dy phn t, mi phn t th ng l 1 con s nguyn c dng qun l 1cluster trn vng d liu. Vic qun l y c th l cho bit cluster t ng ng ang tr ng thi tr ng, h , hay ang ch a ni dung ca 1 tp tin, v cho php xc nh danh schcc cluster cha ni dung ca tp tin. C th dng 1 bng p ng cc nhu cu trn,nh ng cng c th t chc nhiu bng mi bng phc v cho 1 nhu cu.3.2 L do pht s in h

a n i dung tp tin vo a th phi xc nh cc cluster cn tr ng (phn tch (i)), c ni dung tp tin trn a th phi xc nh c danh sch cc cluster ch a ni dung tptin (phn tch (vi)), tuy c th l u thng tin qun l ngay trn cluster nh ng khi truyxut r t chm nn nht thit phi lp ra bng ny qun l truy xut nhanh hn.3.3. Hnh th c t ch c

xc nh cc cluster tr ng, h , hay thu c tr ng thi lun l c bit no (nhngtr ng thi ch mang 1 trong 2 gi tr : C Khng) ta c th qun l theo dng ch mc: mi

phn t ca bng qun l l 1 con s ni ln tr ng thi ca cluster mang ch s t ng ng. mc n gin ta ch cn qun l 2 tr ng thi lun l l cluster tr ng & cluster h . Danhsch cc cluster h c th l u tr c tip (c bao nhiu cluster h th danh sch c b y nhiuphn t), v s cluster h trn a s r t t. Vic qun l cluster tr ng c th dng hnh thcbitmap (mi bit qun l 1 cluster t ng ng): nu mun bit cluster K l tr ng hay khng taxem gi tr ca bit K l 0 hay 1. Ta cng c th qun l vng tr ng bng cch l u 1 danhsch cc ph n t, mi phn t cha v tr bt u & kch th c ca vng tr ng t ng ng.

Vic xc nh mt tr ng thi lun l ca cluster c th thit k kh n gin, vn ch yu l hnh thc t chc c th xc nh chui cc cluster cha ni dung ca 1 tp tin, cmt s hnh thc c bn nh sau:

1. 3.3.1 Lu tr ni dung t p tin trn dy cluster lin ti p ...2. 3.3.2 S d ng c u trc danh sch lin k t ...

3. 3.3.3 S d ng c u trc danh sch lin k t k t h p ch mc:


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Ta t chc 1 bng cc phn t nguyn (dy s nguyn), mi phn t c dng qun l 1 cluster trn vng d liu theo dng ch mc (phn t K qun l cluster K). Vi quinh:. Nu phn t K trn bng c gi tr l FREE th cluster K trn vng d liu ang

tr ng thi tr ng.. Nu phn t K trn bng c gi tr l BAD th cluster K trn vng d liu s c h

thng hiu l tr ng thi h .. Nu phn t K trn bng c gi tr khc FREE v khc BAD th cluster K trn vng

d liu ang cha ni dung ca 1 tp tin. Khi ny ta cn bit c cluster k tip chani dung ca tp tin: nu phn t K ca ba?ng c gi tr L v L = EOF th cluster K lcluster cui cng ca tp tin, nu L EOF th phn k tip ca ni dung tp tin nm ticluster L (qun l theo dng danh sch lin kt).

Nh vy hnh th c t ch c ny c th p ng c t t c cc nhu c u qu n lcluster: xc nh cluster tr ng, h, hay ang ch a n i dung t p tin, v chu i cc cluster ch ani dung c a m t t p tin (khi bi t cluster b t u).

V d, nu ni dung bng qun l Cluster ca a trn nh sau:

Hnh 2.4: Bng qun l Cluster trn a

0 1 2 3 4 5 6 7 8 9 10 11 12 13 ... 1001(cc ph n t t 13 n 1001 u c gi tr l FREE)

th t y c th xc nh lc ny trn a ang c 2 cluster h , 990 cluster trng, 8 clusterchani dung tp tin. C th l:-Cc cluster h : 4, 10

-Cc cluster tr ng: 8, 13, 14, 15, , 1001-Cc cluster cha ni dung tp tin: 2, 3, 5, 6, 7, 9, 11, 12. Trong c 3 tp tin: + tp tin I chim 3 cluster theo ng th t l: 2, 3, 5. + tp tin II chim 1 cluster duy nht l: 6. + tp tin III chim 4 cluster theo ng th t l: 9, 7, 11, 12.

Lu : Phn t u tin ca bng c ch s l 0 nn nu Cluster u tin ca vng DATA c nh ch s l FC > 0 th FC phn t u tin ca bng (t 0 .. FC -1) s khng cdng qun l Cluster, m bo tnh cht ch mc (phn t mang ch s K qun l tr ngthi ca Cluster mang ch s K). Khi ny khng gian b lng ph hon ton khng ng k,nh ng vi c qun l truy xut th tin li hn, ta cng c th tn dng phn khng gian t ngng vi FC phn t u bng ny l u 1 thng tin qun l no .Gi tr c a cc ph n t trn b ng:Ta cn phi t ra 3 gi tr hng c bit l FREE, BAD v EOF t ng ng vi 3 tr ngthi cluster: tr ng, h , ho c l cluster cui ca ni dung tp tin, ta cng c th t thm 1 s gi tr c bit na cho nhng tr ng thi c bit khc ca cluster (nu c) hoc 1 s gi tr dnh ring phc v cho nhng nhu cu trong t ng lai. Nh ng gi tr cn li s t ngng vi tr ng thi cluster ang cha ni dung tp tin v lc gi tr ca phn t cng chnhl ch s ca cluster k tip.

Cc hng c bit (v dnh ring nu c) phi khc vi cc gi tr c th c trn ch s cluster th cluster t ng ng mi c th s dng c. V d, vi hnh trn, nu ta t hngEOF = 7 th tp tin III s b hiu lm l ch chim ng mi cluster 9 ch khng phi chim 4cluster!

Mi phn t trn bng nn l 1 con s nguyn d ng c th qun l c nhiucluster hn, khi ny cc hng c bit nu trn s khng th l s m m phi chim nhnggi tr ln nht c th biu din c, v ch s ca cluster cui cng trn vng DATA buc


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phi nh hn nhng gi tr hng c bit ny. Trong tr ng hp cluster u tin c nhch s l FC v FC > 0 th cng c th s dng cc gi tr 0..FC-1 cho nhng hng c bittrn.

3.4. Kch th c c a b ng qu n l Clu st erMi phn t trn bng l 1 con s nguyn nn pht sinh vn phi l u tr mi s

nguyn bng bao nhiu bit. Ta c th cn c vo ch s cluster cui cng trn vng DATA xc nh gi tr ti a cn biu din c ca mi phn t v gi tr ca cc h ng c bit suy ra s bit ti thiu ca mi phn t, n gin c th dng 16bit hoc 32bit cho miphn t ty theo a c kch th c nh hay ln. Vn phc tp nm ch lm sao xcnh s phn t ca bng, cng nh s cluster trn vng DATA. V khi to (nh dng) a thta ch c kch th c ca a, ch khng c kch th c vng DATA, v khng th t t rakch th c cho n nh v i nhng thnh phn khc. Ta c th gii quyt bng cch gi nhkch th c ca bng l 1 sector & kim chng li xem c hp l hay khng, nu khng thtng dn kch th c ca bng cho n khi hp l.

3.5. T ch c qu n l c lu s te r t rn h iu h nh DOS & Wind ow s 9x

Bng qun l cluster trn DOS & Windows 9x c gi l FAT (File Allocation Table), c t chc theo hnh thc danh sch lin kt kt hp ch mc. Trn DOS mi phn t cabng FAT c biu din bng 1 con s nguyn 12bit hoc 16bit (bng FAT t ng ng ctn l FAT12 hoc FAT16). Trn Windows cng c 2 loi FAT trn v c thm loi FAT32(mi phn t c l u b ng 32bit).

Nu phn t K ca FAT c gi tr L th tr ng thi ca Cluster K l:

Tr ng thi c a Cluster KGi tr ca L

FAT12 FAT16 FAT32Tr ng 0 0 0

H FF7 FFF7 FFFFF7Cluster cui ca tp tin FFF FFFF FFFFFFCha ni dung tp tin vc cluster k sau l L 2 .. FEF 2 .. FFEF 2..FFFFEF

Hnh 1.5 : Tr ng thi ca Cluster K

C mt s gi tr tuy vn thuc phm vi biu din nh ng khng th c vi L (v d, viFAT12 l cc gi tr 1, FF0 .. FF6, FF8 .. FFE), y l cc gi tr dnh ring c d phng c th s dng cho nhng tr ng thi c bit khc ca cluster trong nhng phin bn sauca h iu hnh, khi s vn c c s t ng thch gi a cc phin b n c & mi.Chnh v gi tr 0 c dng biu din tr ng thi cluster tr ng nn s khng th tn ticluster mang ch s 0 trn vng d liu, DOS & Windows nhch s ca cluster u tintrn vng d liu l 2 (FC = 2)

Cng t nhng gi tr t ng ng vi tr ng thi cluster cha ni dung tp tin bng trn,ta c th suy ra s cluster ti a m bng FAT12 c th qun l c l FEE (tc 4078d,ch khng phi l 2

12 = 4096), v FAT16 l FFEE (tc 65518d). Nh v y nu s cluster trn

DATA khng qu 4078 th h thng s dng FAT12 qun l, nu s cluster ln hn 4078nh ng khng qu 65518 th s dng FAT16, v ln hn 65518 th s dng FAT32. Tuynhin l qui c mc nh ca h iu hnh, ta cng c th ch nh loi FAT cn s dng, v d vng DATA c 2004 cluster th dng FAT16 qun l vn c.

Bng qun l cluster r t quan tr ng nn DOS & Windows th ng l u thm N b ngbackup phng trnh h hng (N0, th ng l 1). Cc bng FAT c l u tr k tipnhau trn 1 vng gi l vng FAT.


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Vi bng FAT12, vic truy xut mt phn t hi phc tp: n v truy xut trn RAM l 1byte nh ng m i phn t li c kch th c 1.5 byte. Ta c th xc nh 2 byte t ng ngcha gi tr ca phn t, ly gi tr s nguyn khng du 2byte ti ri dng cc php tonx l trn bit truy xut c con s 1.5 byte t ng ng.

V d, ni dung 12 byte u ca bng FAT l:F0 FF FF 03 40 00

FF7F

FFAB

CDEF

offset 0 1 2 3 4 5 6 7 8 9 A Bth 8 phn t u t ng ng ca bng FAT l:

FF0 FFF 003 004 FFFFF7

DAB

EFC ph nt 0 1 2 3 4 5 6 7V kch th c bng FAT12 l kh nh (ti a 12 sector) nn vic truy xut 1 phn t

c n gin ng i ta th ng c ton b cc sector trn b ng FAT vo 1 vng m r i t vng m ny xy ng ra 1 mng s nguyn 2byte m mi phn t ca mng mang gi tr ca phn t t ng ng trn bng FAT. Khi cn l u bng FAT vo a th l i thc hin thaotc ng c li: t mng s nguyn 2 byte to ra dy byte t ng ng ca FAT a vo vngm v l u vng m vo cc sector ch a FAT trn a.

4. Bng th m c4.1 K hi n i m v RDET (Root Directory Entry Table):

L 1 dy phn t (entry), mi phn t cha tn & cc thuc tnh ca 1 tp tin trn thmc gc ca a (hoc l phn t tr ng ch a thu c v 1 tp tin no ht).V d, nu m hnh thuc tnh tp tin c thit k ch gm cc thnh phn: tn chnh

(chui ti a 4 k t), tn m r ng (chui ti a 2 k t), kch th c tp tin (s nguyn 2byte) th RDET s nh sau:Offset

Hnh 1.6 : RDET

4.2 L do pht si nh khi n i m RDETT phn tch (iii).

4.3 Kch th c RDETS entry trn RDET c qui nh bi ch ng trnh nh dng (format) a, con s

ny s ln hay nh l ty theo dung l ng ca a (nh ng ch c chn l s khng qu ln vs tp tin trn a d rt nhiu th s tp tin th m c gc cng khng nn qu nhiu, s gy kh khn cho vic qun l ca ng i s dng). S entry trn RDET khng bt buc phil 1 gi tr chnh xc m cho php dao ng mt t, v vy ta c th iu chnh hn ch lng ph khng gian l u tr trn sector. V d, nu mi entry c kch th c 32 byte & ta d

nh t chc 50 entry cho RDET th khng hay lm, c th iu ch nh li thnh 48 entry hoc64 entry.


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4.4 C u tr c Entr y c a DOS

ArchiveDirectory aLabelSystemHidden ReadOnly

+ ReadOnly: thuc tnh ch c, khi tp tin c thuc tnh ny h thng s khng chophp sa hoc xa.

+ Hidden: thuc tnh n, tr ng thi mc nh h thng s khng hin th tn ca cctp tin ny khi lit k danh sch t p tin.

+ System: thuc tnh h thng, cho bit tp tin c phi thuc h iu hnh khng + a Label: thuc tnh nhn a, trn RDET ch c ti a 1 entry c thuc tnh ny,

khi entry khngphi t ng ng vi tp tin m c dng cha nhn ca a l1 chui ti a 11 k t c l u 11 byte u tin ca entry

+ Directory: thuc tnh th m c, nu entry c thuc tnh ny th tp tin t ng ngkhng phi l mt tp tin bnh th ng m l mt tp tin th m c. Mi th mc trnDOS c l u tr ging nh m t tp tin bnh th ng, ni dung ca tp tin th m cny l danh mc nhng tp tin v th m c con ca n.

+ Archive: thuc tnh l u tr , cho bit tp tin c backup hay ch a (b ng lnh

backup ca h iu hnh), y l thuc tnh hu nh khng c s dng v t khic nhu cu backup tt c cc tp tin m ch cn l u nh ng tp tin cn thit.Khi ta xa tp tin, entry t ng ng phi c chuyn sang tr ng thi tr ng, nh ng


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tr ng thi tr ng lc ny khng phi l 32 byte ca entry c chuyn sang gi tr 0 m ch cbyte u tin c i thnh E5. V tt c cc k t ca tn tp tin u khng th c m l 0hoc E5 nn bit 1 entry c tr ng hay khng ta ch cn nhn gi tr byte u tin ca entry:nu khc 0 v E5 th khng phi l entry tr ng. Mi khi tm entry tr ng s dng h thng tm theo th t t u tr i nn nu ta gp 1 entry tr ng c byte u l 0 th tt c cc entry pha sau cng l nhng entry tr ng dng ch a t ng uc s dng (32 byte trnentry u l 0)

4.5 B ng th m c co n SDET (Sub Directory Entry Table):4.5.1 Khi ni m:

Mi th mc trn DOS c l u tr ging nh m t tp tin bnh th ng. Ni dung catp tin th m c ny l mt dy entry, mi entry cha tn & thuc tnh ca nhng tp tin vth m c con thuc th mc ang xt ging y nh cc entry trn RDET, dy entry ny cgi l SDET. C th ni mt cch n gin r ng SDET l ni dung ca tp tin th m c.SDET c cu trc t chc ging nh RDET nh ng c l u tr ngay trn vng DATA (v lni dung tp tin). Trn a c ng 1 RDET nh ng c th c r t nhiu SDET v cng cth khng c bng SDET no.

4.5.2 L do pht sinhNu s tp tin trn a c th nhiu th nht thit phi a ra khi nim th mc trnh chuyn tt c mi tp tin trn a phi l u chung vo 1 ni rt kh qun l. V ccthuc tnh ca th m c kh ging vi cc thuc tnh ca tp tin bnh th ng nn c th tra khi nim th m c l mt tp tin c bit v t chc l u tr nh mt tp tin bnh th ng,khng cn phi a ra m t thit k khc cho vic t chc l u tr h thng th m c.4.5.3 Kch th c SDET

S entry trn SDET c th r t nh m cng c th r t ln, ph thuc vo s l ngtp tin & th mc con bn trong th mc an g xt ch khng b qui nh 1 con s c nhnh trn RDET. V SDET nm trn vng DATA nn ti u s entry ca SDET th ng c t sao cho khng b lng ph khng gian trn cluster. V d, nu entry c kch th c32 byte v cluster c c kch th c 32 sector th s entry ca SDET s l bi ca 512.4.5.4 B ng SDET trn DOSLun c 2 entry . v .. u bng m t v chnh th mc ny v th m c cha can. Cu trc mi entry trn SDET cng ging nh entry trn RDET, ch khc s l ngentry & v tr l u gi ni dung entry trn SDET l khng c nh. V SDET lun chim tr ncluster nn thuc tnh kch th c tp tin trn entry t ng ng vi th m c s khng cn s dng v lun c DOS gn l 0. Nh v y khi to 1 th m c th s entrytrong SDET ca th m c s l SC/32 (SC l kch th c cluster), trong entry u tin cphn tn l . v phn cn li l u cc thng tin v th m c ny, entry th hai c phn tn l.. (2 byte u ca entry l u k t . v 9 byte k sau l u kho ng tr ng) v phn cn li l ucc thng tin v th m c cha ca th m c ny, t entry th ba tr i u l entry tr ng(32byte u mang gi tr 0). Nu chp vo trong th m c con ny nhiu hn (SC/32 -2) tptin th bng SDET hin ti khng s entry qun l, khi ny kch th c bng SDET s c h thng cho tng thm bng cch tm cluster tr ng trn vng DATA v l u ni dungcc entry pht sinh thm vo cluster mi ny (v phn cn li ca cluster nu c cng cl u cc entry trng nh trn cluster u tin).

1. 5. Boot Sector2. 5.1 K hi n i m

L sector u tin ca a, cha mt on ch ng trnh nh np h iu hnhkhi khi ng my v cc thng s quan tr ng ca a: kch th c cluster, kch th c bngth mc, kch th c bng qun l cluster, ...5.2 L do pht s in h

Cc bng qun l cluster & bng th mc p ng cc phn tch nu trn,nh ng tht s c th thc hin c cc thao tc truy xut a ta cn phi bit c v tr& kch th c ca tng thnh phn trn a. V a c th c kt ni vo mt h thngkhc nn thng tin v cc thnh phn ca a phi c l u ngay trn chnh a bt


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c h thng no cng c th hiu. Sector u tin ca a l ni thch hp nht cha ccthng tin quan tr ng ny.5.3 Hn h th c t ch c

Cc thng s quan tr ng ch chim 1 kch th c nh nn ta c th qui c mt vngnh trn sector dng cha cc thng s ca a (phn cn li l on ch ng trnh n ph iu hnh khi khi ng), mi thng s c qui nh nm ti mt offset c th c nhno . Trong tr ng hp tng kch th c cc thng s v phn ch ng trnh n p h iuhnh ln hn 512byte th c th dng tip nhng sector k sau l u

5.4 T ch c thng tin trong Boo tSector c a DOS & Window s5.4.1 Boot Sector c a h iu hnh DOSOffset S byte ngha0 (0h) 3 Lnh nhy n u on m Boot (qua khi vng thng s)3 (3h) 8 Tn cng ty /version ca HH11 (0Bh) 2 S byte ca sector13 (0Dh) 1 S sector ca cluster

14 (0Eh) 2 S sector tr c bng FAT16 (10h) 1 S l ng bng FAT17 (11h) 2 S Entry ca RDET19 (13h) 2 S sector ca a21 (15h) 1 K hiu loi a22 (16h) 2 S sector ca FAT24 (18h) 2 S sector 1 track (tnh theo sector)26 (1Ah) 2 S l ng u c (head)28 (1Ch) 4 Khong cch t ni m t a n u a 32 (20h) 4 Kch th c a (n u s 2 byte ti offset 13h l 0)36 (24h) 1 K hiu vt l ca a cha a (0 : mm, 80h: cng)37 (25h) 1 Dnh ring38 (26h) 1 K hiu nhn din HH39 (27h) 4 SerialNumber ca a43 (2Bh) 11 a Label54 (36h) 8 Dnh ring62 (3Eh) 448 on ch ng trnh Boot n p tip HH khi khi ng my510 (1FDh) 2 Du hiu kt thc BootSector /Master Boot (lun l AA55h)

Hnh 1.7 : Boot Sector ca h iu hnh DOS

V d, vi a c na u ca Boot Sector nh sau:EB 3C 90 4D 53 57 49 4E-34 2E 31 00 02 10 01 00 .


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.}.}[email protected] 07 00 CD 10 EB EF A0-FD 7D EB E6 A0 FC 7D EB .........}....}.E1CD 16 CD 19 26 8B 55-1A 52 B0 01 BB 00 00 E8 .....&.U.R......th ta c th suy ra thng tin v cc thnh phn nh sau:. 2 byte t byte trn mi sector ca a l: 0200h = 512d

(byte). Gi tr ca byte t sector trn mi cluster ca a l: 10h = 16d

(sector). 2 byte t sector tr c vng FAT l: 0001h = 1d (sector). Gi tr ca byte t bng FAT ca a l: 02h = 2d (bng). 2 byte t entry trn bng RDET l: 0200h = 512d (entry)

Kch th c bng RDET l 512*32/512 = 32 (sector).. 2 byte t c bng FAT l: 00FFh = 255d (sector). 4 byte t ng s sector trn a l: 000FEEC2h =

1044162d (v 2 byte ti offset 13 u l 00 nn kch th c a c ly 4 byte tioffset 20)

T cc thng s trn ta c th tnh ra c kch th c ca vng h thng l: S sector

tr c FAT + S FAT * Kch thc FAT + Kch th c RDET = 1 + 2*255 + 32 = 543(sector) Vy sector u tin ca vng d liu c ch s l 543, m mi cluster chim 16sector, nn cluster2 s chim 16 sector t 543 n 558, cluster 3 s chim 16 sector t 559 n 574. Tngqut,cluster k s chim 16 sector bt u ti sector c ch s 543 + 16*(k-2)6. Tng kt

M hnh t chc tp tin trn mt a file ca h iu hnh tng qut lun bao gmcc thnh phn chnh l: vng d liu cha ni dung tp tin, th ng c t chc d in v khi (cluster) gm nhiu sector h thng hot ng ti u; vng h thng chacc thng tin qun l, bao gm bng qu n l cluster qun l cc khi trn, bng thmc qun l cc tp tin & cc thuc tnh lin quan, ngoi ra th ng c mt hoc mt s sector cha cc thng tin qun l cc vng trn.Vi cc a c t chc theo dng FAT ca h iu hnh DOS & Windows, ccthnh phn c t chc theo th t nh sau:

... ... ... ...BootSectorArea FAT Area RDET DATA Area

Hnh 2.8 : Th t t chc ca cc thnh ph n

Trn thc t c r t nhiu h iu hnh khc nhau, khng ch l cc h iu hnhtrong my tnh PC m cn c nhng h iu hnh trong my nh s, my quay phim, mythu m, in thoi di ng,... Mi h iu hnh c th t chc h thng tp tin trn a theonhng kin trc khc nhau, nh ng v i nhng thit b l u tr c kch th c khng ln thqun l cluster theo ph ng php danh sch lin k t kt hp ch mc l thch hp, v t ng thch nhau a s h iu hnh u c cu trc a c thit k theo dng FAT nhtrn. C th l a mm, a cng b ti & cc loi th nh (Flash Memory) th ng cnh dng dng FAT v c th s dng trn cc loi my tnh & h iu hnh khc nhau mkhng cn nh dng li theo cu trc trn h thng mi.

Vi a mm 1.44MB bnh th ng th cc thnh phn c phn b c th nh sau:Sector


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Hnh 2.9 Cc thnh phn phn b ca a mm 1.44MB bnh th ng

III. nh dng a cng, a mm, a Flash1. Cc phn tch c n thit

c th l u tr c thng tin /d liu vo h thng l u tr & truy xut, s dng c cc d liu trn h thng l u tr mt cch hiu qu th cn phi tun t thc hincc cng on:1. a ra khi nim tp tin, th mc, a.2. Xy dng m hnh thuc tnh & chc nng trn tp tin & th mc.3. T chc c hnh thc l u tr tp tin /th mc & cc hnh thc qun l cn thit khctrn a.4. Vit thut gii & ch ng trnh th c hin cc chc nng cn thit vi cc tp tin /th m ctrn a.

Cng on th t c th ni ngn gn l ci t cc chc nng trn a, nhngchc nng c bn phi c tr c tin l: nh dng a, chp tp tin vo a, lit k danhsch tp tin trn a, c ni dung tp tin, xa tp tin.2. nh dng a2.1 K hi n i m

a c th s dng c th thao tc u tin phi tin hnh chnh l nh dng

(format) a. Chc nng ny c th do ng i s dng thc hin cng c th do nh s n xuthoc ng i phn phi lm gim ty theo loi thit b. Bi v khi ch a thi hnh chc nngnh dng th a ch l mt dy sector c ni dung rc (nhng gi tr ngu nhin khng ngvi nhng gi tr cn thit theo qui nh), do khng th thc hin c cc thao tc truyxut tp tin trn a v khng bit trn a ang c nhng tp tin no, nm ti u, ch nocn tr ng, kch th c cluster l bao nhiu,...

Nh v y vic nh dng a chnh l xc nh cc thng s ca tng thnh phn trna (v tr, kch th c ca cluster, bng qun l cluster, bng th mc, ...) v a cc gi tr thch hp vo nhng thnh phn . ch ng trnh h iu hnh c th truy xut c 1a bt k th h iu hnh phi cn c vo nhng thng s ny m hiu c t chc tptin trn a, t mi thc hin c cc chc nng chp, xa, xem, s a, ...

Mun c 1 a trng c th s dng bnh th ng th sau khi xc nh v tr & kchth c ca cc thnh ph n qun l, ta cn phi l u cc thng s quan tr ng voBootSector, sau l u vo cc entry trn bng th m c cc gi tr t ng ng vi tr ng thitr ng, cc phn t trn bng qun l cluster cng vy tr cc phn t t ng ng vi cccluster b h (d nhin n u h thng c qun l n tr ng thi cluster h v khi ny ccphn t qun l cluster h cng phi c gn cho cc gi tr ph hp).

Vn c v ln nht trong chc nng nh dng chnh l vic xc nh kch th cbng qun l cluster. V khi thc hin chc nng ny th h thng ch c kch th c a &kch th c sector - cc thng s cn li phi t xc nh. Cc thng s khc c th t phnquyt khng c chnh xc lm cng khng gy nh h ng ln, nh ng kch th c cabng qun l cluster phi c tnh chnh xc m tnh c th phi qua nhng b c llun nht nh ch khng th tnh tr c tip.

Vi mt a c nh dng ta cng c th nh dng li, khi ny c 2 tr ng hp:. nh dng li hon ton (full format): to ra nhng dng thc mi ph hp hn


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cho a, cc thng s ca tng thnh phn trn a s c xc nh li. Chc nng nyd nhin cng c dng cho nhng a ch a c nh dng.

. nh dng nhanh (quick format): chp nhn gi li cc thng s c ca a, ch cpnht li tr ng thi cc cluster ang cha d liu thnh tr ng thi tr ng v cho tt c entrytrn bng th m c gc v tr ng thi tr ng. Chc nng ny t ng ng v i vic xa tt

c mi tp tin & th mc ang tn ti trn a, nh ng th i gian thi hnh r t nhanh cth nhanh hn thi gian xa 1 tp tin!2.2 nh d ng cho a (full format)2.2.1 Thu t gi i:(u vo : tn a, kch th c a, kch th c sector, 2 hm c /ghi sector; u ra : a trngc ni dung BootSector, bng qun l clustor, bng th m c hp l). B c 1: Xc nh gi tr hp l cho cc thng s cn thit ngoi tr kch th c

bng qun l cluster.. B c 2: Tnh kch th c bng qun l cluster da vo cc thng s bit.. B c 3: L u gi tr cc thng s trn vo cc offset qui c trn BootSector.. B c 4: L u gi tr t ng ng vi tr ng thi tr ng vo cc entry trn bng th m c.. B c 5: Kho st cc cluster trn vng d liu xc nh nhng cluster h .. B c 6: L u gi tr t ng ng vi tr ng thi tr ng /h vo cc ph n t trn bng

qun l cluster

2.2.2 nh d ng a theo kin trc FAT12 /FAT16 -B c 1 : T kch th c a (SV) v nhng tiu ch t ra phn quyt gi tr thch hp

cho kch th c cluster (SC), kch th c RDET (SR), s bng FAT (nF), s sector cavng BootSector (SB cn gi l s sector tr c FAT).

o -B c 2 : Tnh kch th c bng FAT (SF) v loi FAT bng hnh thc th &sai da trn ng thc SB + nF*SF +SR + SD = SV

o (gi s SF =1, t suy ra kch th c vng d liu (SD) v kim chng lixem 2 thng s ny c ph hp nhau khng, nu khng hp l th th SF =2,3, 4, ... cho n khi hp l)

-B c 3 : L u gi tr cc thng s trn vo cc offset t 3 36h theo ng v tr & kchth c m t trong bng tham s a.

-B c 4 : To 1 vng m c kch th c (SR * 512) byte mang ton gi tr 0 v l uvo SR sector bt u ti sector (SB + nF*SF )

o -B c 5 : Ghi xung & c ln tng cluster t cluster 2 n cluster SD /SC +1.Nu ni dung c c ging ni dung ghi th cho phn t mang ch s t ngng trn bng FAT gi tr 0, ng c li nu khng ging hoc khng thnhcng trong vic c /ghi th gn cho

o phn t mang ch s t ng ng trn bng FAT gi tr FF7 hoc FFF7 (tytheo loi FAT xc nh b c 2).

-B c 6 : To 1 vng m c kch th c (SF * 512) byte & a cc gi tr ca bngFAT vo vng m r i l u vo SF sector bt u ti sector SB. Nu nF > 1 th l utip vo cc v tr SB + SF , SB + 2*SF ,..., SB + (nF-1)*SF .

* Mt s v d v vic xc nh kch th c bng FAT-V d 1 : Xt a t ng ng trn a m m 1.44MB (c 2880 sector, mi sector c 512 byte), cc tp tin trn a c th truy xut nhanh & an ton hn ta c th cho SC = 4 (sector),SB = 1 (sector), SR = 32 (entry) = 2 (sector), nF = 2.

Thay cc gi tr trn vo ng thc SB + nF*SF +SR + SD = SV ta c 1 + 2SF +2 + SD = 2880 (sector), hay 2SF + SD = 2877 (sector)


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(*) (*) SD < 2877 (sector) = 719.25 (cluster) Loi FAT ti u nh t (v mt kch th c) l FAT12, v SD < 4079 (cluster)

* Gi s SF = 1 (sector): (*) SD = 2877 -2SF = 2875 (sector) = 718.75 (cluster) (v micluster chim 4 sector).

. Vng d liu c 718 cluster, nn bng FAT phi c 718 + 2 = 720 phn t, do SF = (720*1.5)/512 = 2.1x (sector)

. Bng FAT phi chim 3 sector mu thun vi gi thit SF = 1. Vy kch th cbng FAT ca a ny khng th l 1 sector

* Gi s SF = 2 (sector): t ng t , ta vn thy mu thun, tc kch th c bng FATphi ln hn 2 sector.

* Gi s SF = 3 (sector): (*) SD = 2877 -2SF = 2871 (sector) = 717.75 (cluster) (vmi cluster chim 4 sector).

. Vng d liu c 717 cluster, nn bng FAT phi c 717 + 2 = 719 phn t,do SF = (719*1.5)/512 = 2.1x (sector)

. Bng FAT phi chim 3 sector ph hp vi gi thit SF = 3. Vy kchth c bng FAT ca a ny l 3 sector.

-V d 2 : Xt a t ng ng trn a m m 1.44MB (c 2880 sector, mi sector c 512 byte), cc tp tin trn a c th truy xut nhanh & an ton hn ta c th cho SC = 1 (sector),SB = 1 (sector), SR = 224 (entry) = 14 (sector), nF = 2.Thay cc gi tr trn vo ng thc SB + nF*SF +SR + SD = SV ta c 1 + 2SF +14 + SD = 2880 (sector), hay 2SF + SD = 2865(sector) (*) (*) SD < 2865 (sector) = 2865 (cluster)

Loi FAT ti u nh t (v mt kch th c) l FAT12, v SD < 4079 (cluster) * Gi s SF = 1(sector): (*) SD = 2865 -2SF = 2863 (sector) = 2863 (cluster) (v mi cluster chim 1sector).. Vng d liu c 2865 cluster, nn b ng FAT phi c 2865 + 2 = 2867 phn t, do

SF = (2867*1.5)/512 = 8.3x (sector). Bng FAT phi chim 9 sector mu thun vi gi thit SF = 1. Vy kch th c bng

FAT ca a ny khng th l 1 sector

* T ng t , vi SF t 2 n 8 sector ta vn thy mu thun, tc kch th c bngFAT phi ln hn 8 sector.

* Gi s SF = 9 (sector): (*) SD = 2865 -2SF = 2847 (sector) = 2847 (cluster) (vmi cluster chim 1 sector).

) Vng d liu c 2847 cluster, nn bng FAT phi c 2847 + 2 = 2849 phn t, do SF = (2849*1.5)/512 = 8.3x (sector)

) Bng FAT phi chim 9 sector ph hp vi gi thit SF = 9. Vy kch th c bngFAT ca a ny l 9 sector.

-V d 3 : Xt a c kch th c 4000000 sector, ta c th cho SB = 3 sector, SR = 512 entry= 32 sector, nF = 2. Cc thng s c th i sang 1 s gi tr khc cng c, nh ng SCtrong tr ng hp ny khng th phn 1 cch ty tin v s cluster ti a m kin trc FATcho php ch l 65518 (vi tr ng hp FAT16, cn vi FAT12 ch l 4078). V vng h thngc kch th c r t nh nn SD s gn bng SV. Vy SC t nht cng gn bng


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4000000/65518 = 61.xx (sector). y l 1 con s qu ln cho SC, nh ng tha tiuchun SC l ly tha ca 2 th ta phi cho SC=64 sector v d nhin loi FAT c s dng trong tr ng hp ny phi l FAT16 ch khng th dng FAT12.Thay cc gi tr trn vo ng thc SB + nF*SF +SR + SD = SV ta c3 + 2SF + 32 + SD = 4000000 (sector), hay 2SF + SD = 3999965 (sector) (*)

* Gi s SF = 1 (sector): (*) SD = 3999965 - 2SF = 3999963 (sector) = 62499.4x (cluster)(v mi cluster chim 64 sector).. Vng d liu c 62499 cluster, nn bng FAT phi c 62499 + 2 = 62501

phn t, do SF = (62501*2)/512 = 244.1x (sector). Bng FAT phi chim 245 sector mu thun vi gi thit SF = 1. Vy kch

th c bng FAT ca a ny khng th l 1 sector

* T ng t , vi SF t 2 n 244 ta vn thy mu thun, tc kch th c bng FATphi ln hn 244 sector.

* Gi s SF = 245 (sector): (*) SD = 3999965 - 2SF = 3999475 (sector) = 62491(cluster) (v mi cluster chim 64 sector).

. ) Vng d liu c 62491 cluster, nn b ng FAT phi c 62491 + 2 = 62493 phn t, do SF = (62493*2)/512 = 244.1x (sector)

. ) Bng FAT phi chim 245 sector ph hp vi gi thit SF = 245. Vy kch th c bngFAT ca a ny l 245 sector.2.3 nh d ng nhanh (quick form at)2.3.1 Thu t gi i:(u vo : tn a cn format li; u ra : a trng c thng s cc thnh phn qun lkhng thay i)

B c 1: c BootSector xc nh cc thng s cn thit. B c 2: c bng qun l cluster vo b nh. B c 3: Gi nguyn danh sch cc cluster h (n u c) & cho cc tr ng thi cccluster cn li thnh tr ng. B c 4: L u l i bng qun l cluster vo a. B c 5: To 1 vng m c kch th c bng kch th c bng th m c gc & a vo vng m cc gi tr t ng ng vi cc entry tr ng. B c 6: Ghi vng m trn vo v tr l u tr bng th m c gc ca a.

2.3.2 nh d ng a theo kin trc FAT12 /FAT16

-B c 1 : c BootSector xc nh cc thng s SB, SF, nF, SR. -B c 2 : c bng FAT vo mng aFAT trn b nh. -B c 3 : Gn gi tr FREE (gi tr 0) vo cc phn t c gi tr khc BAD (FF7 vi

FAT12 hoc FFF7 vi FAT16) trn mng aFAT. -B c 4 : L u l i mng aFAT trn vo nF bng FAT trn a (lu vo SF sector b t

u t i sector SB, n u nF > 1 th lu ti p vo cc v tr SB + SF , SB + 2*SF ,..., SB +(nF-1)*SF )

-B c 5 : To 1 vng m kch th c SR (byte) c ni dung cc byte u l 0. -B c 6 : L u li vng m trn vo bng RDET trn a (lu vo SR sector bt u

t i sector (SB + nF*SF ) )3. c ni dung tp tin trn a3.1 K hi n i m

y l thao tc truy xut a c thc hin nhiu nht, cng l thao tc th ng


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xuyn ca h thng my tnh. M tc truy xut b nh ngoi (ni cha tp tin) chm hnnhiu so vi b nh trong, do tng tc hot ng ca my tnh ng thi cth bo mt d liu, kim chng s hp l, khng vi cc s c c th gy h h ng, ... khi truy xut tp tin ng i ta th ng dng ti nhiu h thng Cache, nhiu k thut ti u &cc x l khc. Tuy nhin c th d dng hn cho vic nm c mt cch c bn t chc l u tr tp tin & c ch hot ng ca h thng qun l tp tin, cc thut gii ctrnh by sau y ch nu cch gii quyt c bn, chn ph ng nh t - khng quan tm nhiun vic ti u & cc x l nng cao khc.

Ta bit v c bn c 2 loi tp tin khc nhau: tp tin bnh th ng v tp tin thmc (cn gi l th mc con). Cho nn tr c mt c th thy c 2 thao tc khc nhau: cni dung tp tin bnh th ng & c ni dung bng th m c con (tc ni dung tp tin thmc). Nh ng th t ra 1 tp tin bnh th ng cng nh 1 th mc cng c th nm trong 1 thmc con no , v vy c th phn ra ti 4 thao tc t ng i ring bit: c ni dung 1 tptin bnh th ng th m c gc ca a, c ni dung 1 th mc con nm th m c gc caa, c ni dung 1 tp tin bnh th ng 1 th m c con ca a, v c ni dung 1 th mccon nm trong 1 th mc con no ca a.3.2 c n i dung t p t in th m c g c c a a3.2.1 Thu t gi i:(u vo : tn a, tn tp tin cn ly ni dung; u ra : ni dung ca tp tin)

B c 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kchth c c a b ng th mc g c & b ng qu n l cluster, kch th c cluster, v tr b t uc a vng d li u,... ) B c 2: c bng th m c gc vo b nh. B c 3: Tm trn bng th m c gc va c entry c phn tn ging vi tn tp tincn ly ni dung (nu khng c th thng bo t p tin khng t n t i & thot ). B c 4: c bng qun l cluster vo b nh. B c 5: T ni dung bng qun l cluster va c & thng tin ca entry tm c b c 3 suy ra danh sch nh ng cluster cha ni dung tp tin. B c 6: c nhng cluster t ng ng vi danh sch trn & ghp cc ni dung c c li theo ng th t ta c ni dung tp tin (ring ph n n i dung trn clustercui ch l y N byte, v i N = MOD ).

3.2.2 c n i dung t p tin th mc g c c a a c kin trc FAT12 /FAT16 -B c 1 : c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -B c 2 : c bng RDET vo b nh. -B c 3 : Tm trn bng RDET va c entry c phn tn ging vi tn tp tin cn ly

ni dung (nu khng c th thng bo t p tin khng t n t i & thot ).

-B c 4 : c bng FAT vo mng aFAT trn b nh. -B c 5 : T ch s cluster bt u f1 trong entry tm c b c 3 xc nh dy cc

phn t k tip f2, f3, f4 , ... theo cng thc fi+1= aFAT [ fi ]cho n khi gp ch s fN c aFAT[ fN ] = EOF.

-B c 6 : c nhng cluster f1, f2, f3 , ..., fN& ghp cc ni dung c c li theong th t ta c ni dung tp tin (ring ph n n i dung trn cluster fN ch l y Mbyte, v i M = MOD SC ).

3.3 c n i dung m t th m c con th m c g c c a aVic s dng ni dung tp tin bnh th ng v ni dung ca tp tin th m c l hon

ton khc nhau. Nh ng n u t chc l u tr tp tin th m c ging nh tp tin bnh th ng thvic c ni dung bng th mc con cng s ging nh c ni dung tp tin bnh th ng.Ring i vi a c t chc theo cu trc FAT12 /FAT16 th phn ni dung tp tin thmc trn cluster cui cng c s dng ht ch khng nh tp tin bnh th ng c th ch


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chim 1 phn. V cng v vy tr ng trong entry ca tp tin th m c s khng c s dng (lun c gn l 0), d bng th mc c kch th c bao nhiu i n a.3.4 c n i dung t p t in t rong m t th m c con c a a

Entry cha cc thng tin v tp tin cn c s nm trong bng th m c con ca thmc cha tp tin . C th thy mt vn tr c tin l th m c con cha tp tin c th ang nm trong 1 th mc con khc, v th m c con ny li c th nm trong 1 th m c conkhc na. Nh vy c c ni dung tp tin tr c tin ta phi xc nh ng dn nni cha tp tin (l mt dy cc th mc con m th mc tr c l cha ca th m c sau), t ng dn ny ta s ln l t c & phn tch cc bng th mc con cui cng c cbng th m c con ca th m c cha tp tin. Gi s cc th mc con trong ng dn cgi theo th t l th m c con cp 1, th m c con cp 2, ... th hnh thc xc nh nidung ca bng th m c con cp N l:

-Tm entry t ng ng vi th m c con cp 1 trong bng th m c gc v suy cni dung ca tp tin ny (bng th m c con cp 1).

-Tm entry t ng ng vi th m c con cp 2 trong bng th m c con cp 1 trn vsuy c ni dung ca tp tin th m c con cp 2 (bng th m c con cp 2).

o -Tm entry t ng ng vi th m c con cp 3 trong bng th m c con cp 2trn v suy c ni dung ca tp tin th m c con cp 3 (bng th m c concp 3)

-Tm entry t ng ng vi th m c con cp N trong bng th m c con cp (N-1) trnv suy c ni dung ca tp tin th m c con cp N (bng th m c con cp N)

3.4.1 Thu t gi i:(u vo : tn a, ng dn & tn tp tin cn ly ni dung; u ra : ni dung tp tin )

B c 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca cc thmc con cc cp. B c 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kchth c c a b ng th mc g c & b ng qu n l cluster, kch th c cluster, v tr b t uc a vng d li u,... ) B c 2: c bng th m c gc vo b nh. B c 3: c bng qun l cluster vo b nh. B c 4: Bt u t bng th m c gc ln l t suy ra cc bng th m c con cccp k tip & cui cng c bng th m c con cha entry ca tp tin (th m c con cpN) B c 5: Tm trn bng th m c hin ti entry c phn tn ging vi tn tp tin cnly ni dung (nu khng c th thng bo t p tin khng t n t i & thot ). B c 6: T ni dung bng qun l cluster c b c 3 & thng tin ca entry tm c b c trn suy ra danh sch nh ng cluster cha ni dung ca tp tin.

B c 7: c nhng cluster t ng ng vi danh sch trn & ghp cc ni dung c c li theo ng th t ta c ni dung tp tin (ring ph n n i dung trn clustercui ch l y N byte, v i N = MOD ).

Thu t gi i chi ti t cho B c 4: B c 4.1: K = 1. B c 4.2: Tm trn bng th m c hin ti entry c phn tn ging vi tn th m ccon cp K (nu khng c th thng bo ng d n sai & thot ). B c 4.3: T ni dung bng qun l cluster c b c 3 & thng tin ca entrytm c b c trn suy ra danh sch nh ng cluster cha ni dung tp tin th m c concp K. B c 4.4: c nhng cluster t ng ng vi danh sch trn & ghp cc ni dung c c li theo ng th t ta c ni dung bng th m c con ca th m c cp K.


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B c 4.5: Gn bng th mc hin ti l bng th m c con trn B c 4.6: Nu K < N th tng K thm 1 v quay li b c 4.2.

3.4.2 c n i dung t p tin th mc con c a a c kin trc FAT12 /FAT16 -B c 0 : Phn tch ng dn xc nh s cp N & tn cc th mc con cc

cp. -B c 1 : c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -B c 2 : c bng RDET vo b nh. -B c 3 : c bng FAT vo mng aFAT trn b nh. -B c 4 : Bt u t RDET ln l t suy ra cc SDET cc cp k tip cho n khi

c SDET ca th m c con cp N -B c 5 : Tm trn bng SDET trn entry c phn tn ging vi tn tp tin cn ly ni

dung (nu khng c th thng bo t p tin khng t n t i & thot ). -B c 6 : T ch s cluster bt u f1 trong entry tm c b c trn xc nh dy

cc phn t k tip f2, f3, f4 , ...theo cng thc fi+1= aFAT [ fi ]cho n khi gp ch s fN c aFAT[ fN ] = EOF.

-B c 7 : c nhng cluster f1, f2, f3 , ..., fN& ghp cc ni dung c c li theong th t ta c ni dung tp tin (ring ph n n i dung trn cluster fN ch l y Mbyte, v i M = MOD SC ).

Ghi ch: Ta cng c th k t hp cc bc 5,6,7 vo b c 4.3.5 c n i dung th m c t rong m t th m c con c a a

Bi ton ny c gii quyt chc nng k tr c (bng cch thc hin t ucho n ht b c 4).

4. L u gi tp tin vo a

4.1 K hi n i mSau thao tc u tin l nh dng a, chc nng k tip c nh h ng n nidung l u tr trn a l a tp tin vo a, chc nng ny s c thc hin nhiu lntrong qu trnh s dng a. Vic a 1 tp tin vo a c th l chp 1 tp tin t ni khcvo a, to 1 tp tin trn a, hoc to 1 th mc con trn a. Khi a ang tr ng thitr ng th cc thao tc ch c th thc hin trn th m c gc ca a, nh ng khi a cth m c con th nhng thao tc trn c th thc hin trong 1 th mc con no ca a.Ta c th phn ra 4 thao tc t ng i ring bit: a 1 tp tin bnh th ng vo th m c gcca a, to 1 th m c con th m c gc ca a, a 1 tp tin bnh th ng vo 1 th m ccon no ca a, to 1 th mc con trong 1 th mc con no ca a.4.2 a 1 tp tin bnh thng vo th m c g c c a a

4.2.1 Thu t gi i:(u vo : tn a, tn & cc thuc tnh ca tp tin, ni dung tp tin; u ra : tn, cc thuctnh & ni dung tp tin c l u vo a theo ng cu trc l u tr thit k - khng nhh ng n cc ni dung ang c sn trn a)

B c 1: c BootSector ca a xc nh cc thng s cn thit (v tr &kch th c c a b ng th mc g c & b ng qu n l cluster, kch th c cluster, v tr b tu c a vng d li u,... ) B c 2: c bng th m c gc vo b nh. B c 3: Tm trn bng th m c gc va c 1 entry tr ng (nu khng c ththng bo h t ch lu tr & thot ). B c 4: T kch th c tp tin & kch th c cluster xc nh s cluster N mtp tin phi chim (= / ) B c 5: c bng qun l cluster vo b nh.


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B c 6: Tm trn bng N phn t t ng ng vi tr ng thi cluster tr ng (nukhng c N ph n t th thng bo khng dung l ng tr ng lu ni dung t ptin & thot ) B c 7: i u ch nh li gi tr N phn t trn thnh tr ng thi ca cluster chani dung tp tin (theo ng th t )

B c 8: a vo entry th mc tm c b c 3 tn & cc thuc tnh catp tin. B c 9: L u l i entry va iu ch nh vo bng th m c gc ca a. B c 10: L u l i bng qun l cluster vo a. B c 11: Phn ni dung tp tin ra thnh nhng phn c kch th c bng kchth c cluster v l u chng vo N cluster t ng ng vi N phn t tm c b c6.

4.2.2 a mt t p tin vo th mc g c c a a c kin trc FAT12 /FAT16 -B c 1 : c BootSector xc nh cc thng s SB, SF, nF, SR, SC, SS. -B c 2 : c bng RDET vo b nh.

-B c 3 : Tm trn bng RDET va c 1 entry tr ng (nu khng c th thng bo h tch lu tr & thot ). -B c 4 : Xc nh s cluster N m tp tin s chim ( N=/SC ). -B c 5 : c bng FAT vo mng aFAT trn b nh. -B c 6 : Tm trn mng aFAT N phn t f1, f2, ..., fNc gi tr 0 (nu khng c N

ph n t th thng bo khng dung l ng tr ng lu ni dung t p tin & thot ). -B c 7 : iu ch nh li gi tr N phn t trn theo cng thc: aFAT [ fi ] = fi+1, vi i t

1 n (n-1), v aFAT [ fN ] = EOF. -B c 8 : a vo entry th mc tm c b c 3 tn & cc thuc tnh ca tp tin

(tr ng cluster bt u c gn gi tr f1) -B c 9 : L u l i entry va iu ch nh vo RDET ca a. -B c 10 : L u l i mng aFAT trn vo nF bng FAT trn a. -B c 11 : Phn vng ni dung tp tin ra thnh nhng on c kch th c bng SC

v l u chng vo cc cluster t ng ng mang ch s f1, f2, ..., fN trn vng DATA.4.3 T o 1 th m c con th m c g c c a a4.3.1 Thu t gi i:(u vo : tn a, tn & cc thuc tnh ca th m c; u ra : mt th m c r ng c to ratrn th m c gc ca a theo ng cu trc l u tr thit k - khng nh h ng n ccni dung ang c sn trn a)

B c 1: c BootSector ca a xc nh cc thng s cn thit B c 2: c bng th m c gc vo b nh. B c 3: Tm trn bng th m c gc va c 1 entry tr ng. B c 4: c bng qun l cluster vo b nh. B c 5: Tm trn bng 1 phn t t ng ng vi tr ng thi cluster tr ng. B c 6: i u ch nh li gi tr phn t trn thnh tr ng thi ca cluster chani dung tp tin (v l cluster cu i ) B c 7: a vo entry th mc tm c b c 3 tn & cc thuc tnh catp tin th m c. B c 8: L u l i entry va iu ch nh vo bng th m c gc ca a. B c 9: L u l i phn t va iu ch nh b c 6 vo bng qun l clusterca a. B c 10: To 1 vng m c kch th c bng kch th c cluster v a vo


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vng m ni dung ca bng th mc con t ng ng vi 1 th mc r ng B c 11: L u vng m trn vo cluster t ng ng vi phn t tm c b c 6.

4.3.2 T o 1 th mc con trn th mc g c c a a c kin trc FAT12 /FAT16 -B c 1 : c BootSector xc nh cc thng s SB, SF, nF, SR, SC, SS. -B c 2 : c bng RDET vo b nh. -B c 3 : Tm trn bng RDET va c 1 entry tr ng. -B c 4 : c bng FAT vo b nh. -B c 5 : Tm trn bng FAT va c 1 phn t C mang gi tr 0. -B c 6 : iu ch nh li gi tr phn t trn thnh EOF. -B c 7 : a vo entry th mc tm c b c 3 tn & cc thuc tnh ca tp tin

(tr ng cluster bt u c gn gi tr l C) -B c 8 : L u l i entry va iu ch nh vo RDET ca a. -B c 9 : L u l i phn t va iu ch nh b c 6 vo cc bng FAT ca a. -B c 10 : To 1 vng m c kch th c bng SC v a vo vng m ni dung

ca bng th mc con t ng ng vi 1 th m c r ng (2 entry u c tn l . v ..,cc entry cn li u mang gi tr 0.

-B c 11 : L u vng m vo cluster C ca a.

4.4 a 1 tp t in bnh t hng vo 1 th m c con c a a4.4.1 Thu t gi i:(u vo : tn a, ng dn n ni cha tp tin, tn & cc thuc tnh ca tp tin, ni dungtp tin; u ra : tn, cc thuc tnh & ni dung tp tin c l u vo a ng ch & ng cutrc l u tr thit k - khng nh h ng n cc ni dung ang c sn trn a)

B c 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca ccth m c con cc cp. B c 1: c BootSector ca a xc nh cc thng s cn thit (v tr &kch th c c a b ng th mc g c & b ng qu n l cluster, kch th c cluster, v tr b tu c a vng d li u,... ) B c 2: c bng th m c gc vo b nh. B c 3: c bng qun l cluster vo b nh. B c 4: Bt u t bng th m c gc ln l t suy ra cc bng th m c con cc cp k tip & cui cng c bng th m c con cha entry ca tp tin (thmc con cp N)

B c 5: Tm trn bng th m c cp N trn 1 entry tr ng (nu khng c th n ithm 1 cluster tr ng vo n i dung b ng th mc trn ).* B c 6: T kch th c tp tin & kch th c cluster xc nh s cluster N mtp tin phi chim (= / ) B c 7: Tm trn bng qun l cluster c c b c 3 N phn t t ngng vi tr ng thi cluster tr ng (nu khng c N ph n t th thng bo khng dung l ng tr ng lu ni dung t p tin & thot ) B c 8: i u ch nh li gi tr N phn t trn thnh tr ng thi ca cluster chani dung tp tin (theo ng th t ) B c 9: a vo entry th mc tm c b c 5 tn & cc thuc tnh catp tin. B c 10: L u l i entry va iu ch nh vo bng th m c con cp N trn. B c 11: L u l i bng qun l cluster vo a.


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B c 12: Phn ni dung tp tin ra thnh nhng phn c kch th c bng kchth c cluster v l u chng vo N cluster t ng ng vi N phn t tm c b c6.

4.4.2 a mt t p tin vo 1 th mc con c a a c kin trc FAT12 /FAT16 -B c 0 : Phn tch ng dn xc nh s cp N & tn cc th mc con cc


c SDET ca th m c con cp N -B c 5 : Tm trn bng SDET trn 1 entry tr ng (nu khng c th n i thm 1 cluster

tr ng vo n i dung b ng th mc trn ). -B c 6 : Xc nh s cluster N m tp tin s chim ( N=/SC ).

-B c 7 : Tm trn mng aFAT N phn t f1, f2, ..., fNc gi tr 0 (nu khng c N ph n t th thng bo khng dung l ng tr ng lu ni dung t p tin & thot ). -B c 8 : iu ch nh li gi tr N phn t trn theo cng thc: aFAT [ fi ] = fi+1, vi i t

1 n (n-1), v aFAT [ fN ] = EOF. -B c 9 : a vo entry th mc tm c b c 5 tn & cc thuc tnh ca tp tin

(tr ng cluster bt u c gn gi tr f1) -B c 10 : L u l i entry va iu ch nh vo SDET ca th m c con cp N trn. -B c 11 : L u l i mng aFAT trn vo nF bng FAT trn a. -B c 12 : Phn vng ni dung tp tin ra thnh nhng on c kch th c bng SC

v l u chng vo cc cluster t ng ng mang ch s f1, f2, ..., fN trn vng DATA.4.5 T o m t th m c t rong m t th m c con c s n4.5.1 Thu t gi i:(u vo : tn a, ng dn n ni th m c con c sn, tn & cc thuc tnh ca th m ccon cn to; u ra : mt th m c r ng c to ra trong th mc con ch ra theo ngcu trc l u tr thit k - khng nh h ng n cc ni dung ang c sn trn a)

B c 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca ccth m c con cc cp. B c 1: c BootSector ca a xc nh cc thng s cn thit (v tr &kch th c c a b ng th mc g c & b ng qu n l cluster, kch th c cluster, v tr b tu c a vng d li u,... ) B c 2: c bng th m c gc vo b nh. B c 3: c bng qun l cluster vo b nh. B c 4: Bt u t bng th m c gc ln l t suy ra cc bng th m c con cc cp k tip & cui cng c bng th m c con cha entry ca tp tin (thmc con cp N) B c 5: Tm trn bng th m c hin ti 1 entry tr ng. B c 6: Tm trn bng qun l cluster 1 phn t t ng ng vi tr ng thicluster tr ng. B c 7: i u ch nh li gi tr phn t trn thnh tr ng thi ca cluster chani dung tp tin (v l cluster cu i ) B c 8: a vo entry th mc tm c b c 5 tn & cc thuc tnh ca

tp tin th m c. B c 9: L u l i entry va iu ch nh vo bng th m c con hin ti.


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B c 10: L u l i phn t va iu ch nh b c 7 vo bng qun l clusterca a. B c 11: To 1 vng m c kch th c bng kch th c cluster v a vovng m ni dung ca bng th mc con t ng ng vi 1 th m c r ng B c 12: L u vng m trn vo cluster t ng ng vi phn t tm c b c 6.

4.5.2 T o th mc trong 1 th mc con c a a c kin trc FAT12 /FAT16 -B c 0 : Phn tch ng dn xc nh s cp N & tn cc th mc con cc


c SDET ca th m c con cp N -B c 5 : Tm trn bng SDET trn 1 entry tr ng (nu khng c th n i thm 1 cluster

tr ng vo n i dung b ng th mc trn ). -B c 6 : Tm trn mng aFAT va c 1 phn t C mang gi tr 0. -B c 7 : iu ch nh li gi tr phn t trn thnh EOF. -B c 8 : a vo entry th mc tm c b c 5 tn & cc thuc tnh ca tp tin

(tr ng cluster bt u c gn gi tr l C) -B c 9 : L u l i entry va iu ch nh vo SDET ca th m c con cp N trn. -B c 10 : L u l i phn t va iu ch nh b c 7 vo cc bng FAT ca a. -B c 11 : To 1 vng m c kch th c bng SC v a vo vng m ni dung

ca bng th mc con t ng ng vi 1 th m c r ng (2 entry u c tn l . v ..,cc entry cn li u mang gi tr 0.

-B c 11 : L u vng m vo cluster C ca a.IV. Phc hi nguyn trang khi b xo nhm hoc format nhm . 1. Cu d liu b mt

Khi bn xa mt tp tin hay th mc no trong h thng, thc cht lnh ny ch nh du" xa" trong Directory Entry v nhng thng tin lin quan trong File Allocation Table- FAT(vi phn vng nh dng FAT/FAT32) hoc nh du "xo trong Master File Table - MFTEntry (vi phn vng nh dng NTFS). Lc ny, cc vng (cluster) cha d liu ca tp tinxem nh trng v c tnh l dung l ng ch a dng n ca a cng mc d d liu vntn ti. Khi d liu mi c ghi vo, lc ny d liu c mi thc s b xa i v ghi bngd liu mi. Chng ta (v c h iu hnh) u khng th "nhn" thy c nhng d liu bnh du xa nh ng nhng phn mm cu d liu vn nhn thy chng khi qut qua b mta. V vy chng ta mi cn n nhng phn mm ny trong vic khi phc d liu. C rt nhiu phn mm gip bn thc hin vic ny, t min ph cho n c ph nhOntrack Easy Recovery, Winternals Disk Commander, Active Uneraser, PC Inspector FileRecovery, Drive Rescue... Mi phn mm u c nhng im mnh- yu ring, nh ng nhnchung, kh nng "cu h" ty thuc rt nhiu vo cu trc d liu trn a cng v nhngthao tc c nh h ng n cc vng d liu. 2. Cu trc d liu trn a Tr c tin, chng ta cng tham kho qua cch thc thng tin ca mt tp tin c l u trtrn a cng. Vi phn vng FAT, d liu c l u tr ti 3 ni trn a cng, bao gm:

Directory Entry cha thng tin v tp tin gm tn, dung l ng, thi gian to v s hiucluster u tin cha d liu ca tp tin; FAT cha s hiu cc cluster c s dng cho


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tp tin v cc cluster cha d liu ca tp tin (vng Allocation). Vi phn vng NTFS, d liu c l u tr trong MFT (Master File Table) Entry v vng Allocation (hnh minh ha). Bt k phn mm cu d liu no cng c gng tm li nhng thng tin t 3 ni ny cth khi phc y ni dung ca mt tp tin, nu thiu (hoc mt) mt trong nhng thngtin ny, d liu khng ton vn hoc khng th khi phc (xem bng). Nh vy, xem xt cc tr ng hp trn th kh nng khi phc d liu th ng kh thp.Tr ng hp cc cluster ca Allocation b hng hoc b chp , bn hu nh khng th khiphc c v d liu b xa v chp bi d liu mi. V l thuyt, bn vn c th lyli d liu c vi k thut MFM (Magnetic Force Microscope) tuy nhin k thut ny khng c p dng rng ri trn thc t v mt nhiu thi gian v chi ph rt cao.

Allocation DirectoryEntry FAT

Tp tin c khi phc y

-Tp tin c khi phc nh ng c th ni dungkhng y hoc khng th c c.

- Tp tin c th c khi phc nh ng khng y thng tin -

- Khng th khi phc d vn c th nhn thy tnca tp tin. - -

- - Khng th khi phc v khng cn du vt catp tin

- - -

Allocation MFT

Tp tin c khi phc y

- Tp tin c th c khi phc nh ng khng y thng tin

- Khng th khi phc d vn c th nhn thy tn ca tptin.

antoanthongtin end

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