EET 450 – Advanced Digital Chapter 10 Hard Disk Drives.
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Transcript of EET 450 – Advanced Digital Chapter 10 Hard Disk Drives.
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EET 450 – Advanced Digital
Chapter 10 Hard Disk Drives
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Interface Info Ultra2 SCSI
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Interface Speed
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Other Interface Technologies SCSI
Fast SCSI Ultra SCSI Wide Ultra SCSI Ultra2 SCSI Wide Ultra2 SCSI Ultra3 SCSI
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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
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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
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Other Interfaces Advanced Technology Attachment
(ATA) AKA Ultra DMA or IDE
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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)
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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
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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
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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
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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
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Heads Contact heads Inductive heads (gap) Magneto-resistive heads (read only) Write pre-compensation
Changes strength of field due to greater density toward hub
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Head actuator Band stepping
Original – crude Servo-voice coil Dual actuator
Uses multiple head advantage
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Other characteristics Landing Zone
Crash zone Park/lock
Hold head during movement of drive itself
Thermal compensation
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Geometry Tracks Cylinders Sectors
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Physical Format Sector ID Sector interleave
Latency due to rotation Cylinder skewing Addressing
Cyl/head/sector give absolute address
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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
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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)
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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
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Performance Access time
Time to get to data Data Transfer Rate Disk Caching
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Special Drives AV Drives Cartridge drives
SyQuest Bernoulli Jazz
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Alternate Tech Magneto-Optical Phase Change Disks
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Installation Physical
Mounting location Power Setup & Operation
BIOS Low-Level format
• G=C800:5
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Installation Partitioning Formatting