Hard Disk Storage

1
Hard Disk Storage

• A hard disk drive contains rigid, disk-shaped
  platters, usually constructed of aluminum or
  glass
• Also known as a Fixed Disk
• Grown rapidly in size and performance and have
  dropped dramatically in price over recent years

2
Hard Disk Drive Operation

• consists of spinning disks with heads that move
  over the disks and store data in tracks and
  sectors
• heads read and write data in concentric rings
  called tracks, which are divided up into segments
  called sectors

3
Hard Drive Anatomy

• Disk platters
• Logic board
• Read/write heads and Spindle motor
• Cables and connectors
• Head actuator mechanism
• Configuration items (such as jumpers or switches)

4
S.M.A.R.T

• Stands for Self-Monitoring, Analysis and
  Reporting Technology
• Industry standard providing failure prediction
  for disk drives
• According to Seagate, 60 of drive failures are
  mechanical, which are exactly the type of
  failures S.M.A.R.T. is designed to predict.

5
Caching

• Has a major effect on disk drive performance
• Can be software (Smartdrv in DOS or Vcache in
  Windows)
• Can be hardware
• Many IDE and SCSI drives have cache memory built
  directly into the drives on-board controller

6
The IDE Interface

• A generic term applied to any drive with an
  integrated (built-in) disk controller
• The IDE interface as we know it is officially
  called ATA (AT Attachment) and is an ANSI
  standard
• Placing the controller on the drive gives IDE
  drives an inherent reliability advantage over
  interfaces with separate controllers

7
IDE Controllers

• Many people who use systems with IDE connectors
  on the motherboard believe that a hard disk
  controller is built into their motherboard. Its
  actually part of the drive
• The IDE connector on motherboards in many systems
  is nothing more than a stripped-down bus slot

8
IDE Bus Versions

• XT IDE (8-bit ISA)
• AT Attachment (ATA) IDE (16-bit ISA)
• MCA IDE (16-bit Micro Channel
• Only the ATA version is used today

9
ATA Standards

• ATA-1
• ATA-2
• ATA-3
• ATA-4 (ATAPI)
• ATA-5 (ATAPI)

10
The SCSI Interface

• Stands for Small Computer System Interface
• General purpose interface used for connecting
  many types of devices to a PC
• Many PC manufacturers have standardized SCSI for
  high-end systems (fast, up to 160Mb per second!)

11
SCSI Standards

• Standard SCSI
• Fast SCSI
• Fast-20(Ultra)
• Fast-40(Ultra2)
• Fast-80(Ultra3)

12
Termination

• Improper termination still is one of the most
  common problems in SCSI installations
• Three popular types of termination
• Passive
• Active (also called Alternative 2)
• Forced Perfect Termination

13
SCSI Drive Configuration

• More complicated than IDE drives
• Need to set SCSI ID setting and Terminate any
  open resistors
• Most SCSI host adapters are factory-set to ID 7
  or 15
• Setting the ID usually involves changing jumpers
  on the drive

14
SCSI Versus IDE

• IDE drives usually cost less than SCSI drives
  (popular for home or budget PCs)
• SCSI allows for smoother multitasking and
  increased overall data throughput (popular for
  high end workstations or servers