EET 450 – Advanced Digital

Chapter 10 Hard Disk Drives

Interface Info Ultra2 SCSI

Interface Speed

Other Interface Technologies SCSI

Fast SCSI Ultra SCSI Wide Ultra SCSI Ultra2 SCSI Wide Ultra2 SCSI Ultra3 SCSI

Other Interfaces Fibre Channel – Arbitrated Loop (FC-

AL) 100MB/sec Up to 127 devices up to 10km apart Allows hot swapping Can be dual ported for up to 200

MB/sec

Other Interfaces Serial Storage Architecture

128 devices Up to 10km apart Throughput up to 160 MB/sec Data rates of 90 MB/s in non-RAID and

85MB/s in Raid mode

Other Interfaces Advanced Technology Attachment

(ATA) AKA Ultra DMA or IDE

Other Interfaces CompactFlash/CF+ Type II

Up to 4 Mb and above IBM has a new Microdrive Technology

(1” disk) with capacity up to 340 Mb (7x CF)

Electro-mechanical Combination of electronics and a

mechanical system Mechanical section provides

ROTATION of media and STEPPING of head. Rotation is constant 3600 rpm original (synchronous) Current 5400 or 7200 rpm

Characteristics Latency

Time delay from R/W command until head is positioned

In milliseconds Data Transfer Rate

Transfer of data from HD to computer interface

In megabytes per second

Platters The number of physical media disks

inside the HD Substrate – normally aluminum now

• Rigid base for magnetic coating Area Density

Amount of data packed into an area of disk

Megabits per square inch

Magnetic coating Oxide Media – iron oxide Thin Film Contamination causes ‘bad spots’

Read/Write heads Fly above the surface of the magnetic media 10-12 micro-inches originally Now 5 micro-inches

Heads Contact heads Inductive heads (gap) Magneto-resistive heads (read only) Write pre-compensation

Changes strength of field due to greater density toward hub

Head actuator Band stepping

Original – crude Servo-voice coil Dual actuator

Uses multiple head advantage

Other characteristics Landing Zone

Crash zone Park/lock

Hold head during movement of drive itself

Thermal compensation

Geometry Tracks Cylinders Sectors

Physical Format Sector ID Sector interleave

Latency due to rotation Cylinder skewing Addressing

Cyl/head/sector give absolute address

Physical Format CHS addressing

Limited by design – 1024 cylinders, 255 heads, 63 sectors

Sector Translation Logical Block addressing

Doesn’t follow CHS Sector remapping

Lock out bad sector

File System File Allocation Table

FAT Clusters

• See tables 10.1 and 10.2 capacity versus cluster size

• Smallest chunk of drive used Compression NTFS – New Technology File System

(NT)

Capacity Limits table 10.3Limit Bytes cause

10 Mb 10,485,760 Hardware design

16 Mb 16,777,216 12-bit FAT

32 Mb 33,554,432 # of FAT entries

128 Mb 134,217,728 2KB cluster size

528 Mb 528,482,304 ATA vs BIOS

2 Gb 2,147,483,648 16-bit FAT

8 Gb 8,589,934,592 24-bit LBA addr

Performance Access time

Time to get to data Data Transfer Rate Disk Caching

Special Drives AV Drives Cartridge drives

SyQuest Bernoulli Jazz

Alternate Tech Magneto-Optical Phase Change Disks

Installation Physical

Mounting location Power Setup & Operation

BIOS Low-Level format

• G=C800:5

Installation Partitioning Formatting