Understanding RAID level-5

RAID level-5 requires a minimum of three hard disk drives. This RAID level stripes data and parity across all drives in the array. When an array is assigned RAID level-5, the capacity of the array is reduced by one drive (for data-parity storage).

RAID level-5 is generally the most desirable choice, because it offers both data protection and increased throughput. RAID level-5 gives you higher capacity than RAID level-1, but RAID level-1 offers better performance.

The RAID level-5 requires a minimum of three drives and, depending upon the stripe-unit size, supports a maximum of eight or 16 drives.

RAID level-5 example

You have four physical drives.
Create an array with three physical drives, leaving the fourth as a Hot-spare drive.
Then, create a logical drive within the array.

The data is striped across the drives, creating blocks.

Notice that the storage of the data parity (denoted by the ) also is striped, and it shifts from drive to drive.

A parity block () contains the data from the other blocks in the same stripe.

If a hard disk drive fails in the array, the ServeRAID controller switches read and write requests to the remaining functional drive in the RAID level-5 array.

See also

Selecting a RAID level
RAID level-0
RAID level-1
RAID level-1 Enhanced
RAID level-5 Enhanced