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- A RAID (Redundant Array of Inexpensive Disks) is a very expensive (10K$
for cheapo things and up to 500K$ and more for large high-end) container
- RAIDs support redundancy - i.e. the same data is stored on more then one
physical disk, so a single disk failure does not stop I/O.
- RAIDs normally have multiple controllers, for high-availability and
for load-balancing. A giant RAID might have 20 such controllers...
- RAIDs allow defining virtual disks, each exposed as a separate LUN,
and support LUN masking.
- Finally, mid-range and high-end RAIDs support applications such as
taking snapshots of LUNs, remote mirroring, etc.