IBM ServeRAID-4 Ultra160 Series, User Reference

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Then, create a logical drive within that array.
The data is striped across the drives, creating
blocks.
Notice that the stripe labeled
.
is the data
stripe and the stripe labeled
..
is the copy of
the preceding data stripe. Also notice that
each block on the mirror stripe is shifted one
drive.
1 2
6
3
5
4
1
4 6
5
3
2
*
*
**
**
With RAID level-1E, if one of the physical drives fails, the ServeRAID controller
switches read and write requests to the remaining functional drives in the RAID
level-1E array.
Understanding RAID level-5
RAID level-5 requires a minimum of three physical drives. This RAID level stripes
data and parity across all drives in the array. When you assign RAID level-5 to an
array, the capacity of the array is reduced by the capacity of one drive (for
data-parity storage).
RAID level-5 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.
RAID level-5 requires a minimum of three drives and, depending upon the level of
firmware and the stripe-unit size, supports a maximum of 8 or 16 drives.
The following illustration is an example of a RAID level-5 logical drive.
Start with four physical drives.
Chapter 3. Understanding RAID technology
19