Understanding RAID technology
RAID is the technology of grouping several hard disk drives in a computer into an  array that you can define as one or more logical drives. Each  logical drive appears to the operating system as a single drive. This grouping technique greatly enhances logical-drive capacity and performance beyond the physical limitations of a single hard disk drive.
When you group multiple physical hard disk drives into a logical drive, the ServeRAID controller can transfer data in parallel from the multiple drives in the array. This parallel transfer yields data-transfer rates that are many times higher than with nonarrayed drives. This increased speed makes the system better able to meet the  throughput (the amount of work in a given amount of time) or productivity needs of the multiple-user network environment.
The ability to respond to multiple data requests provides not only an impressive increase in throughput, but also a decrease in response time. The combination of parallel transfers and simultaneous responses to multiple requests allows disk arrays to provide a high level of performance in network environments.