EET 450 – Advanced Digital Chapter 10 Hard Disk Drives.
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Transcript of EET 450 – Advanced Digital Chapter 10 Hard Disk Drives.
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