RAID Levels
15
RAID-1: Mirrored Pair
In the RAID-1 configuration, two disk modules can be bound as a mirrored
pair. In this disk configuration, the SP duplicates (mirrors) the data records
and stores them separately on each disk module in the pair. The disks in a
RAID-1 pair cannot be split into its individual units (as can a software mirror
composed of two individual disk units).
Features of this RAID level include
•
fault tolerance
•
automatic mirroring: no commands are required to initiate it
•
physical separation of images
•
faster write operation than RAID-5
With a RAID-1 mirrored pair, the storage system writes the same data to
both disk modules in the mirror, as shown in Figure 1-10.
Figure 1-10
RAID-1 Mirrored Pair (Hardware Mirrored Pair)
To achieve the maximum fault tolerance, configure the mirror with each disk
module on a different internal SCSI bus; for example, the primary image on
A0, the secondary image on B0, and so on.
First module
Second module
2
0
1
4
3
. . .
2
0
1
4
3
. . .
= User data
(primary image)
= User data
(secondary image)
