Ram lesson Key points

Ø  The disk controller interface governs the maximum data transfer rate. IDE, SCSI and ESDI are roughly twice as fast as the traditional ST-506 interface.

Ø  The speed of a disk drive depends mainly on its access time. Drivers with access times of  25ms or less are generally  considered fast.

Ø  IDE drives are good choice for all single-user machines that need disks up to 500  Mbytes. Over 500 Mbytes, and  for network file servers, the choice is between ESDI or SCSI.

Ø  ESDI drives are simple and  standardized. SCSI drives are more  sophisticated and so potentially higher performing  but they are less standard.

Ø  Sector interleave  is used to  match the data  transfer rate of the controller and processor  to the maximum transfer rate of the disk. Too little sector interleave  is far worse than  too much.

Ø  A catching  disk controller provides the ultimate in disk performance  and it is  the natural partner for MCA or EISA bus machines.

Ø  Software  disk catching, or the use of a RAM disk, provides useful speed gains in disk access but uses main memory.

 Disk fragmentation slows disk operations but can be  avoided by using a defragmentation utility. Incipient disk errors can also cause a disk to slow down