HP P3410A - NetRAID 1M RAID Controller Installation And Configuration Manual page 24

Chapter 2
RAID 5: Striping with Distributed Parity
RAID 5 is the most common configuration because it provides good overall
performance and data protection with a minimum loss of storage capacity.
RAID 5 distributes the parity blocks equally among all disk drives. If you have
five physical drives configured as one RAID 5 logical drive, data blocks are
written as follows:
Disk 1
Stripe 1 Block 1
Stripe 2
Block 5
Stripe 3 Block 9
RAID 5 outperforms RAID 1 for read operations. The write performance,
however, may be slower than RAID 1, especially if most writes are small and
random. For example, to change Block 1 in the diagram above, the
HP NetRAID-1M or 2M adapter must first read Blocks 2, 3, and 4 before it can
calculate Parity Block 1-4. Once it has calculated the new Parity Block 1-4, it
must write Block 1 and Parity Block 1-4.
RAID 5 Advantages
There is no data loss or system interruption due to disk failure, because if
one disk fails, data can be rebuilt.
Capacity equivalent to only one disk in the RAID 5 logical drive is reserved
to store redundant data.
RAID 5 outperforms RAID 1 for read operations.
RAID 5 gives good performance if you have a high volume of small, random
transfers.
RAID 5 Disadvantages
Write performance is slower than RAID 0 or RAID 1.
RAID 5 Summary
Choose RAID 5 if cost, availability, and performance are equally important.
RAID 5 performs best if you have I/O-intensive, high read/write ratio
applications such as transaction processing.
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Disk 2 Disk 3
Block 2 Block 3
Block 6 Block 7 Parity 5-8
Block 10
Parity 9-12
RAID Overview
Disk 4 Disk 5
Block 4 Parity 1-4
Block 8
Block 11 Block 12