In data striping, he data is segmented in equal-size partitions distributed over multiple disks. The size of the partition is called the striping unit.
The partitions are usually distributed using a round-robin algorithm:
if the disk array consists of D disks, then partition i is written in to disk ( i mod D ).
Consider a striping unit equal to a disk block. In this case, I/O requests of the size of a disk block are processed by one disk in the array.
If many I/O requests of the size of a disk block are made, and the requested blocks reside on different disks, we can process all requests in parallel and thus reduce the average response time of an I/O request.
Since the striping unit are distributed over several disks in the disk array in round robin fashion, large I/O requests of the size of many continuous blocks involve all disks. We can process the request by all disks in parallel and thus increase the transfer rate.