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Asif Jamal disk (it)


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Asif Jamal disk (it)

  1. 1. ›  Topic : Introduction Of Computer Asif Jamal Lecturer Management Science National University Of Modern Languages (NUML)
  2. 2. Hard Disks ›  Low-level format- organizes both sides of each platter into tracks and sectors to define where items will be stored on the disk. ›  Partitioning: divide hard disk into separate areas called partitions; each partition functions as if it were a separate hard disk drive. ›  High-level format defines the file allocation table (FAT) for each partition, which is a table of information used to locate files on the disk.
  3. 3. Storage Systems › Hard Drives ›  2 Types: SCSI and IDE › IDE drives- ›  originally developed as alternative to more expensive SCSI drives. ›  Modern versions called EIDE drives. ›  Support up to 4 multigigabyte drives. ›  If you want more devices, use SCSI or USB ›  Low-level formatted at the factory
  4. 4. Low Level Formatting ›  Low level format scans disk for defects and sets aside sectors with defects so they are not used for data. ›  IDE drives should never be low level formatted by a user or technician. Only high level format necessary.
  5. 5. Installing IDE/EIDE drives ›  IDE supports TWO drives in a system ›  one master (boot disk) and one slave ›  set master and slave using jumpers ›  EIDE supports FOUR drives per system ›  2 drives on each of 2 cables ›  only one master, all others are slaves ›  IDE and EIDE drives both use 40-pin ribbon cable aligned to pin 1
  6. 6. Hard Drive
  7. 7. Floppies ›  Two sizes ›  3.5 inch ›  5.25 inch ›  3.5 inch holds 1.44 MB for High density and 750 KB for Double Density ›  Connected with 34 pin ribbon cable ›  Two Floppy Drives possible ›  Has twist in cable to distinguish A drive from B drive
  8. 8. SCSI › Pronounced Scuzzy › Small Computer Systems Interface › For wide range of peripheral devices, including hard disks, tape drives, optical drives, CD-ROMs and disk arrays. › 8 devices can connect to a daisy chain › This chain must be terminated at both ends › Each device on chain is assigned unique device ID number that is determined by jumpers or DIP switches
  9. 9. Installing and configuring SCSI ›  SCSI bus supports 8 devices ›  There are eight SCSI IDs numbered 0 through 7 ›  ID 7 is always reserved for the SCSI host adapter ›  SCSI hard disk, if used as a boot drive, is assigned SCSI ID 0 ›  If you have both IDE and SCSI hard drive, IDE drive should be boot drive
  10. 10. Types of SCSIs ›  SCSI 1- 5 MB transfer rate, Centronics 50 pin or DB 25, has 8 bit bus ›  SCSI 2 -also SCSI Fast Wide, includes 16 bit bus , called Wide SCSI, and twice as fast transfer rate ›  SCSI 3- Includes Ultra SCSI, Wide Ultra SCSI, and Ultra 2 SCSI, 16 bit bus with up to 80 MBps transfer rate
  11. 11. RAID ›  Redundant Array of Independent Disks ›  Category of disk drives that employs 2 or more drives in combination for fault tolerance (error recovery) ›  10 levels of RAID ›  3 on test will be: ›  RAID 0, RAID 3, RAID 5
  12. 12. RAID continued ›  RAID 0- Striped disk without parity ›  RAID 3- Parallel transfer with parity ›  RAID 5- Data striping with parity
  13. 13. How Data is Organized on Disk ›  Tracks- ›  circular areas of the disk ›  Length of a track one circumference of disk ›  Over 1000 on a hard disk ›  Data first written to outer most track ›  Sectors- ›  Divides tracks sections ›  On a floppy 9 sectors exits ›  Cylinders- ›  Logical groupings of the the same track on each disk surface in a disk unit ›  Clusters- ›  Groups of sectors used by operating system ›  64 sectors in one cluster
  14. 14. Track= concentric circle Sector = small arc of track Can store 512 bytes Tracks and sectors
  15. 15. Interleaving ›  Allows the read/write head to use the rotation of the disk to its advantage ›  One sector is written to and the disk skips to several sectors down
  16. 16. Formatting ›  Low level formatting done at factory ›  Builds the File Allocation Table (FAT) ›  Physically scans the disk media for defects ›  Remember FAT is always located at Track 0 ›  High level formatting is automatically done during installation of operating system
  17. 17. Operating System File Systems ›  DOS uses FAT ›  Windows 3.x uses Virtual FAT ›  Win 95 uses VFAT and FAT32 ›  Win NT uses NTFS
  18. 18. Partitioning ›  FDISK command is used ›  Divides hard drive into logical subdivisions which are seen by the operating system as separate logical hard disks. ›  Hard drives divided into primary and extended partitions. The primary partition boots the system. Can have up to 4 primary partitions
  19. 19. Partitioning ›  Extended can be divided up to 23 times on disk. ›  Partitioning disks improves disk efficiency through reduced cluster size. ›  In DOS, Win 3x and early versions of Win 95 a hard disk over 2 GB must be divided into smaller partions ›  Now Win 95 and Win 98 can create a primary partition of up to 8 GB ›  Following partition, the first sector on cylinder 0 reserved for master boot record
  20. 20. Disk compression ›  Reduce amount of space taken up by files by substituting codes for repeating patterns of data ›  To access data on compressed disk, must load disk compression utility into RAM first ›  This disk compression utility works between OS and disk controller to intercept requests and compress or decompress files- the result is slower disk access
  21. 21. Backing up data ›  Archival: full backup- contains everything from the hard disk ›  Incremental: contains only files that have been modified since last (previous) backup ›  Differential: backs up all the data modified since last full backup ›  Copy backup: copy duplicate of file, directory, or disk to another disk
  22. 22. CD ROM ›  Capacity of 650 MB ›  Transfer speeds of around 24X speed ›  X refers to the transfer speed in the first CD ROM, which was 150 K ›  CD is the slowest device on PC ›  When installing to IDE system must be configured as slave ›  WORM and EO