Understanding Raid Level-5 - IBM Netfinity ServeRAID-3H Installation And User Manual

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 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 level of firmware and the
stripe-unit size, supports a maximum of eight or 16 drives.
The following illustration is an example of a RAID level-5 logical drive.
You start with four physical drives.
Create an array using three of the physical drives,
leaving the fourth as a hot-spare drive.
Then, create a logical drive within that array.
The data is striped across the drives, creating blocks.
Notice that the storage of the data parity (denoted by
also is striped, and it shifts from drive to drive.
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A parity block ( ) contains a representation of the data
from the other blocks in the same stripe.
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