Raid Levels - HP Surestore Disk Array 12h - And FC60 Service Manual

using a 5-disk RAID 5 volume group, a stripe segment size of 32 blocks (16
ensure that an entire I/O would fit on a single stripe (16
The total stripe size is the number of disks in a volume group multiplied by the stripe
segment size. For example, if the stripe segment size is 32 blocks and the volume group
comprises five disks, the stripe size is 32 X 5, or 160 blocks (81,920 bytes).

RAID Levels

RAID technology uses a number of different techniques for storing data and maintaining
data redundancy. These industry-standard RAID levels define the method used for
distributing data on the disks in a volume group. Volume groups that use different RAID
levels can be created on the same disk array.
The Disk Array FC60 supports the following RAID levels:
•
RAID 0
•
RAID 1
•
RAID 0/1
•
RAID 3
•
RAID 5
RAID 0
RAID 0 uses disk striping to achieve high performance. Data is striped across all disk in the
volume group. The ability to access all disks in the volume group simultaneously provides a
high I/O rate.
Unlike the other RAID levels, RAID 0 does not provide any data redundancy, error
recovery, or other high availability features. Consequently it should not be used in
environments where high-availability is critical. which is why it is not supported. RAID-0
provides enhanced performance through simultaneous I/Os to multiple disk modules. A
RAID 0 group configuration for a logical disk unit offers fast access instead of high
availability. Software mirroring the RAID-0 group provides high availability.
Figure 18 illustrates the distribution of user and parity data in a four-disk RAID 0 volume
group. The the stripe segment size is 8 blocks, and the stripe size is 32 blocks (8 blocks
times 4 disks). The disk block addresses in the stripe proceed sequentially from the first
disk to the second, third, and fourth, then back to the first, and so on.
Disk Array High Availability Features
48
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