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1 William Stallings Computer Organization and Architecture Chapter 5 Memori External.

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Presentasi berjudul: "1 William Stallings Computer Organization and Architecture Chapter 5 Memori External."— Transcript presentasi:

1 1 William Stallings Computer Organization and Architecture Chapter 5 Memori External

2 2 Jenis Memori External zMagnetic Disk yRAID yRemovable zOptical yCD-ROM yCD-Writable (WORM) yCD-R/W yDVD zMagnetic Tape

3 3 Magnetic Disk zMetal atau plastic dilapisi dg material yg bersifat magnet (iron oxide) zJenis kemasan yFloppy yWinchester hard disk yRemovable hard disk

4 4 Format dan Organisasi Data zLingkaran konsentris atau track yAda Gap antar track yGap sempit, kapasitas bertambah yJumlah bit per track sama (kerapatan bervariasi) yKecepatan putar tetap zTrack dibagi menjadi beberapa sector zUkuran minimum block adalah satu sector zSatu block bisa berisi lebih dari satu sector

5 5 Fixed/Movable Head Disk zFixed head yAda satu head (r/w) per track yHead diletakkan pada tangkai yg tetap zMovable head yHanya ada satu head per side yDiletakkan pada tangkai yg dpt bergerak

6 6 Removable / Nonremovable zRemovable disk yDapat dilepas dari drive dan diganti dg disk lain yMemberikan kapasitas simpanan yg tak terbatas yMudah melakukan transfer data antar sistem zNonremovable disk yTerpasanang permanen dalam drive

7 7 Floppy Disk z8”, 5.25”, 3.5” zKapasitas kecil ysampai 1.44Mbyte (ada yg 2.88M) zLambat zUmum dipakai zMurah

8 8 Winchester Hard Disk (1) zDikembangkan oleh IBM di Winchester (USA) zDikemas dalam satu unit zBerisi satu cakram atau lebih zHead sangat kecil zHandal

9 9 Winchester Hard Disk (2) zUmum digunakan zMurah zSbg external storage yg sangat cepat zKapasitas semakin besar yDalam orde GB

10 10 Removable Hard Disk zZIP yMurah yBanyak digunakan y100MB zJAZ yMahal y1G zL-120 (a: drive) yJuga dpt untuk membaca 3.5” floppy

11 11 Pencarian Sector zHarus dapat mengenali awal suatu track dan sector zFormat disk yMenambahkan informasi tambahan yMemberi tanda awal track dan sector

12 12 Gap1 IdGap2DataGap3 Gap1 IdGap2DataGap3 Track Sync Byte HeadSectorCRC Sync Byte DataCRC ST506 format (old!)

13 13 Karakteristik zFixed head atau movable head zRemovable disk atau fixed disk zSingle side atau double side zSingle platter atau multiple platter zMekanisme head yContact (Floppy) yFixed gap yFlying (Winchester)

14 14 Multiple Platter zSatu head per side zSemua head di-join dan di-align zTrack-track yg setiap platter membentuk cylinder zData dipecah berdasarkan cylinder yMengurangi gerakan head yMeningkatkan kecepatan (transfer rate)

15 15 Kecepatan zSeek time ygerakan head ke track yg dituju z(Rotational) latency yPutar platter sampai posisi data dibawah head zAccess time = Seek + Latency zTransfer rate

16 16 RAID zRedundant Array of Independent Disks zRedundant Array of Inexpensive Disks zAda 6 level zTidak berhirarki zSejumlah disks (fisik) yg dipandang sbg satu drive (logical) oleh Sistem Operasi zData tersebar diantara disk fisik

17 17 RAID 0 zNo redundancy zData striped across all disks zRound Robin striping zIncrease speed yMultiple data requests probably not on same disk yDisks seek in parallel yA set of data is likely to be striped across multiple disks

18 18 RAID 1 zMirrored Disks zData is striped across disks z2 copies of each stripe on separate disks zRead from either zWrite to both zRecovery is simple ySwap faulty disk & re-mirror yNo down time zExpensive

19 19 RAID 2 zDisks are synchronized zVery small stripes yOften single byte/word zError correction calculated across corresponding bits on disks zMultiple parity disks store Hamming code error correction in corresponding positions zLots of redundancy yExpensive yNot used

20 20 RAID 3 zSimilar to RAID 2 zOnly one redundant disk, no matter how large the array zSimple parity bit for each set of corresponding bits zData on failed drive can be reconstructed from surviving data and parity info zVery high transfer rates

21 21 RAID 4 zEach disk operates independently zGood for high I/O request rate zLarge stripes zBit by bit parity calculated across stripes on each disk zParity stored on parity disk

22 zLanjut minggu depan 22

23 23 RAID 5 zLike RAID 4 zParity striped across all disks zRound robin allocation for parity stripe zAvoids RAID 4 bottleneck at parity disk zCommonly used in network servers

24 24 Optical Storage CD-ROM zOriginally for audio z650Mbytes giving over 70 minutes audio zPolycarbonate coated with highly reflective coat, usually aluminum zData stored as pits zRead by reflecting laser zConstant packing density zConstant linear velocity

25 25 CD-ROM Drive Speeds zAudio is single speed yConstant linier velocity y1.2 ms -1 yTrack (spiral) is 5.27km long yGives 4391 seconds = 73.2 minutes zOther speeds are quoted as multiples ze.g. 24x zThe quoted figure is the maximum the drive can achieve

26 26 00 FF x 10 Min Sec Sector Mode Data Layered ECC 12 byte Sync 4 byte Id 2048 byte288 byte 2352 byte CD-ROM Format zMode 0=blank data field zMode 1=2048 byte data+error correction zMode 2=2336 byte data

27 27 Random Access on CD-ROM zDifficult zMove head to rough position zSet correct speed zRead address zAdjust to required location

28 28 CD-ROM for & against zLarge capacity (?) zEasy to mass produce zRemovable zRobust zExpensive for small runs zSlow zRead only

29 29 Other Optical Storage zCD-Writable yWORM yNow affordable yCompatible with CD-ROM drives zCD-RW yErasable yGetting cheaper yMostly CD-ROM drive compatible

30 30 DVD - what’s in a name? zDigital Video Disk yUsed to indicate a player for movies xOnly plays video disks zDigital Versatile Disk yUsed to indicate a computer drive xWill read computer disks and play video disks

31 31 DVD - technology zMulti-layer zVery high capacity (4.7G per layer) zFull length movie on single disk yUsing MPEG compression zFinally standardized (honest!) zMovies carry regional coding zPlayers only play correct region films zCan be “fixed”

32 32 DVD - Writable zLoads of trouble with standards zFirst generation DVD drives may not read first generation DVD-W disks zFirst generation DVD drives may not read CD- RW disks zWait for it to settle down before buying!

33 33 Foreground Reading zCheck out optical disk storage options zCheck out Mini Disk

34 34 Magnetic Tape zSerial access zSlow zVery cheap zBackup and archive

35 35 Digital Audio Tape (DAT) zUses rotating head (like video) zHigh capacity on small tape y4Gbyte uncompressed y8Gbyte compressed zBackup of PC/network servers


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