• RAID-0: “Striped.” Disks are combined into one physical device where reads and writes of data are done in parallel. Access speed is fast but there is no redundancy.
• RAID-1: “Mirrored.” Fully redundant, but the size is limited to the smallest disk.
• RAID-4: “Parity.” For N disks, 1 disk is used as a parity bit and the remaining N−1 disks are combined. Protects against a single disk failure but access speed is slow since you have to update the parity disk for each write. Some, but not all,
files may be recoverable if two disks fail.
• RAID-5: “Striped-Parity.” As with RAID-4, the effective size is that of N−1 disks. However, since the parity information is also distributed evenly among the N drives the bottleneck of having to update the parity disk for each write is avoided. Protects against a single disk failure and the access speed is fast.
For more info.. go through this paper:
http://www.slac.stanford.edu/econf/C0303241/proc/papers/TUDT004.PDF
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