Chapter 2
RAID Overview
18
RAID 10 Disadvantages
•
Costs are high, because 50% of all disk space is allocated for redundancy.
•
Capacity expansion is an offline operation only.
RAID 10 Summary
•
RAID 10 provides the best performance for most applications where
redundancy and large logical drive size are required, and cost is not a factor.
RAID 50: Spanning with Distributed Parity
A RAID 50 configuration combines multiple RAID 5 arrays into a single storage
space. A distributed parity algorithm within each RAID 5 array provides data
redundancy. The data is striped across all the RAID 5 arrays that constitute the
RAID 50 logical drive. For example, if your RAID 50 configuration spans two
RAID 5 arrays, data blocks are written as follows:
Spanned Array (RAID 50)
Array 1 (RAID 5)
Array 2 (RAID 5)
Disk
1
Disk
2
Disk
3
Disk
4
Disk
5
Disk
6
Disk
7
Disk
8
Stripe
1
Block
1
Block
2
Block
3
Parity
1-3
Block
4
Block
5
Block
6
Parity
4-6
Stripe
2
Block
7
Block
8
Parity
7-9
Block
9
Block
10
Block
11
Parity
10-12
Block
12
Stripe
3
Block
13
Parity
13-15
Block
14
Block
15
Block
16
Parity
16-18
Block
17
Block
18
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:
♦
With the HP NetRAID-1M adapter, the total number of disks in the
RAID 50 logical drive is limited by the number of disks that can be
attached to its single SCSI channel. For example, if a Rack Storage/12
enclosure is used, the maximum number of disks in a RAID 50 logical
drive is 12.