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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
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

disk jargon
Disk jargon
  • Latency seek time (to get to track) plus
  • wait tune (
  • 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

data is recorded on thin layer of magnetic material
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

removable winchester disk drive
Removable “Winchester” disk drive
  • IBM 30MB 3340
  • 1973
  • Heads and platters
  • encased in a
  • sealed unit

COCO magdisk

36 gb 10 000 rpm 10 platter disk ibm
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

recording head
Recording Head

COCO magdisk

flying read write head air bearing slider
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

recording density gb in 2 against year
Recording density (Gb/ in2 against year)

Compound Annual Growth Rate

COCO magdisk

working of hard disk
Working of hard disk
  • Working of hard disk

COCO magdisk

nomenclature
Nomenclature

COCO magdisk

disk geometry
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

platter size
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

windows disk organization
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

fundamental principles
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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