RAID Controller Card Overview

The function of the RAID Controller (shown in Figure below ) is to combine multiple disk drives into an array of disk drives to obtain performance, capacity, and reliability that exceeds that of a single large drive. Th e array of drives appears to the host computer as a single logical drive.

Striping can be done at the byte level, or in blocks. Byte-level striping means that the file is broken into "byte-sized pieces", The first byte of the file is sent to the first drive, then the second to the second drive, and so on. Sometimes byte-level striping is done as a sector of 512 bytes. Block-level striping means that each file is split into blocks of a certain size and those are distributed to the various drives. The size of the blocks used is also called the stripe size (or block size, or several other names), and can be selected from a variety of choices when the array is set up.