hard disk

							 INSIDE HARD DISK…
Prepared By :
Internal Structure
Internal Structure Contd…




     R/W Head
Storing Data
               A Gray Code is a binary code
               in which successive numbers
               differ by only a single bit.
               A 3-bit Gray Code is shown
               below :

                         000
                         001
                         011
                         010
                         110
                         111
                         101
                         100
Storing Data Contd…

                A typical track is shown in
                yellow; a typical sector is shown
                in blue.
                A sector contains a fixed
                number of bytes -- for example,
                256 or 512.
                Either at the drive or the
                operating system level, sectors
                are often grouped together into
                clusters.
Hard Disk Types
•Internal Hard Disk Drive :
        General Used Hard Disk Drives i.e. in Home PCs

•External Hard Disk Drive :
          An external hard drive sits outside the main computer tower
in its own enclosure. The enclosure is slightly larger than the hard
drive itself, and sometimes contains a cooling fan.
Hard Disk Interfaces
•IDE (ATA / PATA / ATAPI / UDMA)
   •Integrated Device Electronics (Advanced Technology Attachment)
   •Enhanced IDE
   •Used in home PCs
•SCSI
   •Small Computer System Interface
   •Requires SCSI Controller
   •Ultra160 and Ultra320 SCSI standards
   •Suitable for Servers

•SATA
   •Serial ATA with higher data transfer rate
   •Available now widely for home PCs
Parallel ATA Interface




     Ribbon Connectors with 40-pin schematic
        Serial ATA Interface




SATA ports on a motherboard A 15-pin SATA cable   A 7-pin SATA cable
Interface Choices Summary
•Parallel: Set up is easy. External. Slow.
•USB: Set up is very easy. Good performer. Hot swappable.
Requires Windows 98 and higher.
•IDE. Set up is moderately difficult. Requires opening your PC
and connecting some cables inside. Performance is much better
than parallel- or USB-devices.
•IEEE 1394 FireWire: Set up is easy. Excellent performer.
Costly. Requires Windows 98 and higher.
•SCSI: Set up is even more difficult than for IDE. Best
performer. Best when multiple devices are used. Generally
needs a separate SCSI card.
•PC Card: Set up is easy. Good performance. For notebook use
only(small version of PCI slot in PC motherboard).
Some Pics from HDD inside…




      Read/Write heads on the disk platters
Some Pics from HDD inside…




           Particle Catcher
Some Pics from HDD inside…




        Accutator Controls R/W Head
Some Pics from HDD inside…




      Platters removed with Accutator
Some Pics from HDD inside…




       Close-up look of the R/W head
Some Pics from HDD inside…




            Air Filter
Some Pics from HDD inside…