Data storage devices

1
Data storage devices

• Unit objectives
• Describe hard drives and file systems, and
  install IDE and SCSI hard drives
• Describe optical data storage, install and use
  optical drives and discs
• Install and use floppy drives and disks, and
  install, use, and safely remove USB flash drives
• Maintain and troubleshoot your data storage
  devices

2
Hard drive components
The mechanism that moves the heads very
precisely Into position over the magnetic
tracks written on the platters
Magnetic devices that both read and write data
on the platters.
Metal or plastic disks on which the magnetic
material Is coated. Data is recorded in that
magnetic material as magnetically polarized
regions
The axis , or central hub, around which the
platters spin
3
Hard drive geometry
The logical collection of all the tracks at a
given distance from the axis
Data is written in a series of concentric tracks
Each track is divided into sectors. Each sector
contains identification info at Its beginning
and end , and contains Data in between. Sectors
hold 512bytes of Data. Sectors are gathered
into groups called Clusters. Clusters contain
between 4 and 64 sectors each.
4
Head crash

• Heads contact surface during operation
• Heads float ½ of a millionth of an inch above
  surface
• Dont drop or jolt your PC during operation
• Heads parked at shutdown, damage still possible

5
File systems

• Logical organization scheme for files
• Sector and cluster sizes
• How file and folder names are tracked
• How file and folder locations are tracked
• How files and folders are stored within clusters
• FAT and NTFS

6
FAT (File Allocation Table) file system

• Developed for DOS
• Supported through current Windows versions
• 16 and 32 bit versions (FAT16 and FAT32
  respectively)
• 16-bit version featured restricted file names (8
  characters, 3 letter extensions, no spaces, no
  punctuations)
• Slow and limited compared to NTFS

7
NTFS file system (Windows NT File System)

• Developed for Windows NT
• Supported in Windows 2000 Professional and all
  Windows XP versions
• 32-bit file system
• 255-character names with spaces
• Supports larger files, larger volumes, and is
  faster than FAT

8
FAT vs. NTFS
9
Directory trees

• Root directory
• Directories contain file and folders
• Directory folder
• FAT16 limited root directory to 512 entries

10
Root directory of C
11
File organization problems

• Best speed when file is contiguous
• Files become fragmented (distributed across the
  disk)
• Defragging relocates file parts to be contiguous
• Cluster chain can be broken
• By viruses or poorly written programs
• Use chkdsk or other utility to check and fix file
  problems.

12
Physical installation

• Set drive identification jumpers or switches
• Install the drive into the PC chassis
• If SCSI and required, terminate drive
• Connect data and control cables
• Connect the power cable

13
ATA drive identification

• Drive jumpers
• Cable position

14
SCSI drive identification

• Set jumpers switches

15
Chassis installation

• Use any available bay for hard drive
• Also smaller specific hard drive bays
• Install where data and power cables reach
• Mount horizontally or vertically
• Use ESD precautions

16
Data and power cable connections

• Most cables are keyed
• Older cable
• Wire 1 red stripe
• Pin 1 labeled with number or triangle
• Line up wire 1 with pin 1
• Correct connector for master/slave
• Terminate SCSI bus
• IDE/SCSI
• Large peripheral power connector with triangular
  corners
• SATA
• Specialized keyed power connector

17
Hard drive preparation

• Low-level format
• Partition
• High-level format

18
Low-level formatting

• Records tracks
• Divides tracks into sectors
• Old drives required occasionally re-low-level
  formatting
• New drives, done at the factory
• New drives ZBR

19
Partitioning

• Divides disk into logical drives
• Logical drives volumes
• First sector on bootable volume is the Master
  Boot Record (MBR)

20
Unpartitioned disk in Windows
21
Partition types

• Master boot record (MBR)
• Primary and extended
• Primary directly accessed by OS
• Extended contain one or more logical drives that
  are accessed by the OS
• Up to 4 primary and 1 extended per drive
• Basic and Dynamic
• Basic standard type since DOS
• Dynamic new type with Windows 2000
• Permits changes without restarting the operating
  system

22
Partitioning utilities

• fdisk
• fdisk /mbr (rewrites the MBR)
• Windows Disk Manager
• Third-party

23
Formatting

• Creates logical file storage structures
• File allocation table and so forth
• Destructive process
• Sometimes you can recover data
• Use format command or Windows Disk Management