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DISK STORAGE

DISK STORAGE. IBM 305 RAMAC, 1956 5 MB on 50 24-inch disks 9 Kbits/s transfer rate. Before 1956, computers had core memory, multi-track mag tape, and drums. Installed size of office suites and disk capacity. Disk jargon. Latency seek time (to get to track) plus

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DISK STORAGE

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  1. DISK STORAGE • IBM 305 RAMAC, 1956 • 5 MB on 50 24-inch disks • 9 Kbits/s transfer rate Before 1956, computers had core memory, multi-track mag tape, and drums. COCO magdisk

  2. Installed size of office suites and disk capacity COCO magdisk

  3. Disk jargon • Latency seek time (to get to track) plus • wait tune (<half a revolution) 2-200 ms • Transfer rate MB/sec without arm movement • hundreds of MB/s • Platter One or two recording surfaces • RPM Revolutions per minute (thousands) • Capacity Gigabytes • Track density • Linear (or recording) density COCO magdisk

  4. Data is recorded on thin layer of magnetic material flying read and write head Al Hoagland gn’s former boss Max today: ~333 GB per platter 120 MB/s transfer rate 15,000 rpm (2 ms latency) COCO magdisk

  5. Removable “Winchester” disk drive • IBM 30MB 3340 • 1973 • Heads and platters • encased in a • sealed unit COCO magdisk

  6. 36 GB 10,000 RPM, 10-platter disk (IBM) <1 cent per MB Storage cost 1 million percent less than 20 years ago (67% per year) All the heads are mounted on the same assembly, and move together. COCO magdisk

  7. Longitudinal vs. Perspendicular recording COCO magdisk

  8. Recording Head COCO magdisk

  9. Flying read/write head (air bearing slider) http://www.hitachigst.com/tech/techlib.nsf/techdocs/AE7AEDB327B2E21186256D330078799B/$file/Femto_white_paper_FINAL_082505.pdf HGA=Head Gimbal Assembly COCO magdisk

  10. Recording density (Gb/ in2 against year) Compound Annual Growth Rate COCO magdisk

  11. Kryder’s Law – growth of hard drive capacity COCO magdisk

  12. Working of hard disk • Working of hard disk COCO magdisk

  13. Nomenclature COCO magdisk

  14. DISK GEOMETRY • Tracks and cylinders • Formatting marks the beginning and end of 512-byte sectors • (it takes up to 20% • of capacity) • (there are far more tracks than shown) COCO magdisk

  15. Platter size • Platter diameters: • 5.12” old PCs • 3.74” current PCs • 3.00” 10,000 rpm drives • 2.50” 15,000 rpm drives 34MB Microdrive • 1.80” PC card • 1.30” obsolete PCMCIA • 1.00 CompactFlash (cameras, pocket-PCs, …) COCO magdisk

  16. Windows disk organization • Boot Master Record (including Partition Table) • track (cylinder) 0, side (head) 0, sector 1 • loads the operating system • File Allocation Table (FAT) • manages free clusters • Root Folder (directories) • Data Area COCO magdisk

  17. Fundamental Principles • Tape, drum and disk storage are based on Faraday’s Law: change in magnetic field induces voltage • Magnetic disk is a direct-access block-storage device.(large capacity, fast transfer, long latency( O/S exploits these characteristics) • Each bit consists of a few hundred magnetic grains. • Access time limited by mechanical motion (head travel to track and rotational speed) • Periphery of disk must not break the sound barrier. • Recording density limited by distance to R/W head.Heads fly a few nanometers above surface. • Sooner or later, solid-state storage will win out. COCO magdisk

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