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Why Use RAID-5?
RAID-5 is a fault-tolerant flavor of RAID that can be understand as “RAID-0 striping with parity”. RAID-5 offers an attractive blend of performance along with resilience in the face of a drive failure:
- Offers performance approaching that of RAID-0 striping.
- Efficient blend of speed/space: capacity of one (1) drive is used for parity; for example, a 4-drive RAID-5 offers the capacity of three drives.
- Tolerates the failure of one drive.
- Can be restored to fault tolerance quickly by replacing a failed drive.
- Ideal for very large data stores where downtime and restoration are problematic (e.g. schedule/deadlines).
- Highly attractive for usages like storing video and other larger data sets where high capacity is needed with some degree of fault tolerance.
- Distributes the parity data across the drives (RAID-4 is similar to RAID-5, but dedicates a drive to parity).
RAID-5 requires at least 3 drives , but an ideal number tends to be 4 drives (roughly triple speed at the loss of capacity of only one drive).
Even a 3-drive RAID-5 is quite attractive (capacity of 2 drives) or a 5-drive RAID-5 (capacity of 4 drives).
At 6 drives or more, the risk profile rises (probability of a drive failure), but even 8 drives might be acceptable for some purposes (RAID-6 offers dual parity drives, and perhaps future software RAID will support that).