HP D5970A - NetServer - LCII Configuration Manual page 22

Chapter 2
RAID 50: Spanning with Distributed Parity
In RAID 50 configurations, parity blocks are distributed throughout the logical
drive that spans two, three, or four arrays. (RAID 50 is a RAID 5 configuration
with array spanning.) If your RAID 50 logical drive has two arrays with four
physical drives each, data blocks are written as follows:
Disk
1
Stripe Block
1
1
Stripe Block
2 7
Stripe Block
3 13
RAID 50 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 each array of the RAID 50 logical drive is
required to provide redundancy.
RAID 50 lets you create large logical drives. You can span up to four arrays
containing a maximum of 12 to 16 physical drives.
RAID 50 gives good performance if you have a high volume of small, random
transfers.
RAID 50 Disadvantages
Capacity expansion is an offline operation only.
Performance is slower than RAID 0 or RAID 10.
RAID 50 Summary
Choose RAID 50 if you need a large logical drive size, and cost, availability, and
performance are equally important. RAID 50 performs best for I/O-intensive,
high read/write ratio applications such as transaction processing.
16
Array 1
Disk Disk Disk
2 3 4
Block Block
Parity
2 3
1-3
Block Block
Parity
8 9
7-9
Block Block
Parity
14 15
13-15
RAID Overview
Array 2
Disk Disk Disk
5 6 7
Block Block Block
Parity
4 5 6
Block Block Block
Parity
10 11
10-12
Block Block Block
Parity
16 17
16-18
Disk
8
4-6
12
18