1 Computer Organization and Architecture Chapter 5 Memori External 7/1/2014 Materi ke 5 Memory External by kustanto

2 Jenis Memori External zMagnetic Disk yRAID yRemovable zOptical yCD-ROM yCD-Writable (WORM) yCD-R/W yDVD zMagnetic Tape 7/1/2014 Materi ke 5 Memory External by kustanto

3 Magnetic Disk zMetal atau plastic dilapisi dg material yg bersifat magnet (iron oxide) zJenis kemasan yFloppy yWinchester hard disk yRemovable hard disk 7/1/2014 Materi ke 5 Memory External by kustanto

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 7/1/2014 Materi ke 5 Memory External by kustanto

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 7/1/2014 Materi ke 5 Memory External by kustanto

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 External Memory 7/1/2014 Materi ke 5 Memory External by kustanto

7 Floppy Disk z8”, 5.25”, 3.5” zKapasitas kecil ysampai 1.44Mbyte (ada yg 2.88M) zLambat zUmum dipakai zMurah 7/1/2014 Materi ke 5 Memory External by kustanto

8 Winchester Hard Disk (1) zDikembangkan oleh IBM di Winchester (USA) zDikemas dalam satu unit zBerisi satu cakram atau lebih zHead sangat kecil zHandal 7/1/2014 Materi ke 5 Memory External by kustanto

9 Winchester Hard Disk (2) zUmum digunakan zMurah zSbg external storage yg sangat cepat zKapasitas semakin besar yDalam orde GB 7/1/2014 Materi ke 5 Memory External by kustanto

ORGANISASI DISK MAGNETIK

11 Pencarian Sector zHarus dapat mengenali awal suatu track dan sector zFormat disk yMenambahkan informasi tambahan yMemberi tanda awal track dan sector 7/1/2014 Materi ke 5 Memory External by kustanto

12 Gap1 IdGap2DataGap3 Gap1 IdGap2DataGap3 Track Sync Byte HeadSectorCRC Sync Byte DataCRC ST506 format (old!) 7/1/2014 Materi ke 5 Memory External by kustanto CRC (Cyclical Redundancy Check), digunakan untuk memverifikasi data yang error akibat gangguan jaringan, distorsi,Cyclical Redundancy Check Pesan error ini biasanya terjadi ketika PC atau laptop mencoba untuk membaca data dari media penyimpanan yang rusak, seperti hard disk, CD, atau DVD

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) 7/1/2014 Materi ke 5 Memory External by kustanto

14 Multiple Platter zSatu head per side zSemua head di-join dan di-align zTrack-track yg setiap platter membentuk cylinder zData dibagi berdasarkan cylinder yMengurangi gerakan head yMeningkatkan kecepatan (transfer rate) 7/1/2014 Materi ke 5 Memory External by kustanto

15 Kecepatan zPencarian waktu (Seek time) ygerakan head ke track yg dituju z(Rotational) latency yPutar platter sampai posisi data dibawah head zAccess time = Seek + Latency zTransfer rate 7/1/2014 Materi ke 5 Memory External by kustanto

16 RAID (Redundant Array of Independent Disks) zAda 6 level zTidak berhirarki zSejumlah disks (fisik) yg dipandang sbg satu drive (logical) oleh Sistem Operasi zData tersebar diantara disk fisik 7/1/2014 Materi ke 5 Memory External by kustanto

17 RAID 0 zNo redundancy zData striped across all disks zBergaris bulat (Round Robin striping) zMeningkatkan kecepatan (Increase 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 7/1/2014 Materi ke 5 Memory External by kustanto

18 RAID 1 zMirrored Disks zData is striped across disks z2 copies of each stripe on separate disks zRead from either (baik) zWrite to both zRecovery is simple ySwap faulty disk & re-mirror yNo down time zExpensive 7/1/2014 Materi ke 5 Memory External by kustanto

19 RAID 2 zDisks are synchronized zError correction calculated across corresponding bits on disks zMultiple (beberapa) parity disks store Hamming code error correction in corresponding positions zLots of redundancy yExpensive yNot used 7/1/2014 Materi ke 5 Memory External by kustanto

20 RAID 3 zmirip (Similar) to RAID 2 zHanya 1 disk yang berlebihan, tanpa memperdulikan seberapa besar arraynya (Only one redundant disk, no matter how large the array) zSederhana paritas bitnya untuk setiap bit yang sama (Simple 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 7/1/2014 Materi ke 5 Memory External by kustanto

21 RAID 4 zEach disk operates independently zTingkat permintaan I/O baik (Good for high I/O request rate) zGarisnya besar (Large stripes) zBit by bit parity calculated across stripes on each disk zPenyimpanannya di atas parity disk (Parity stored on parity disk) 7/1/2014 Materi ke 5 Memory External by kustanto

22 RAID 5 zLike RAID 4 zBergaris di semua disk paritas (Parity striped across all disks) zRound robin allocation for parity stripe zMenghindari kemacetan RAID 4 pada parity disk (Avoids RAID 4 bottleneck at parity disk) zUmumnya untuk server (Commonly used in network servers) zN.B. DOES NOT MEAN 5 DISKS!!!!! 7/1/2014 Materi ke 5 Memory External by kustanto

23 Optical Storage CD-ROM zOriginally for audio z650Mbytes giving over 70 minutes audio zBiasanya Dilapisi almunium (Polycarbonate coated with highly reflective coat, usually aluminum) zData stored as pits zRead by reflecting laser zKepadatan packing konstan (Constant packing density) zConstant linear velocity (kecepatan linear konstan) 7/1/2014 Materi ke 5 Memory External by kustanto

24 CD-ROM Drive Speeds zAudio is single speed yKecepatan konstan (Constant linier velocity) y1.2 ms -1 yTrack (spiral) is 5.27km long yGives 4391 seconds = 73.2 minutes zKecepatan lainnya adalah kelipatannya (Other speeds are quoted as multiples) ze.g. 24x zAngka kecepatan max dapat dicapai (The quoted figure is the maximum the drive can achieve) 7/1/2014 Materi ke 5 Memory External by kustanto

25 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 7/1/2014 Materi ke 5 Memory External by kustanto

26 Random Access on CD-ROM zBerat (Difficult) zPerpindahan head kasar (Move head to rough position) zSet correct speed zRead address zMemerlukan lokasi (Adjust to required location) 7/1/2014 Materi ke 5 Memory External by kustanto

27 CD-ROM for & against zLarge capacity (?) zMudah diproduksi masal (Easy to mass produce) zRemovable zRobust or strong zExpensive for small runs zLambat (Slow) zRead only 7/1/2014 Materi ke 5 Memory External by kustanto

28 Other Optical Storage zCD-Writable yWORM y Terjangkau (Now affordable) yCompatible with CD-ROM drives zCD-RW yDapat dihapus (Erasable) ysemakin murah (Getting cheaper ) ySebagian besar kompatibel (Mostly CD-ROM drive compatible) 7/1/2014 Materi ke 5 Memory External by kustanto

29 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 7/1/2014 Materi ke 5 Memory External by kustanto

30 DVD - technology zMulti-layer zVery high capacity (4.7G per layer) zFull length movie (film) on single disk yUsing MPEG compression zFinally standardized (honest!) zMovies carry regional (daerah) coding zPlayers only play correct region films zCan be “fixed” 7/1/2014 Materi ke 5 Memory External by kustanto

31 Magnetic Tape zSerial access z Lambat (Slow) zVery cheap zBackup and archive 7/1/2014 Materi ke 5 Memory External by kustanto

32 Digital Audio Tape (DAT) zUses rotating head (like video) zHigh capacity on small tape y4Gbyte uncompressed y8Gbyte compressed zBackup of PC/network servers 7/1/2014 Materi ke 5 Memory External by kustanto

End of Session Memory External 7/1/2014Materi ke 333