HP Surestore Disk Array 12h - And FC60 Service Manual page 51

of the pair. If both disks fail or become inaccessible simultaneously, the data on the volume
group becomes inaccessible.
Figure 20 illustrates the distribution of data in a four-module RAID 0/1 volume group. The
disk block addresses in the stripe proceed sequentially from the first pair of mirrored disks
(disks 1 and 2) to the second pair of mirrored disks (disks 3 and 4), then again from the first
mirrored disks, and so on.
Figure 20 Volume Group
RAID 0/1
RAID 3
RAID 3 uses parity to achieve data redundancy and disk striping to enhance performance.
Data is distributed across all but one of the disks in the RAID 3 volume group. The
remaining disk is used to store parity information for each data stripe. A RAID 3 volume
group consists of three or more disks. For highest availability, the disks in a RAID 3 volume
group must be in different enclosures.
If a disk fails or becomes inaccessible, the disk array can dynamically reconstruct all user
data from the data and parity information on the remaining disks. When a failed disk is
replaced, the disk array automatically rebuilds the contents of the failed disk on the new
Disk Array High Availability Features
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