HSG80 ACS Solution Software V8.6 for IBM AIM Installation and Configuration Guide

Planning Storage 2–15
The relationship between the chunk size and the average request size determines if striping
maximizes the request rate or the data-transfer rate. You can set the chunk size or use the
default setting (see “Chunk Size,” page 2–26, for information about setting the chunk
size). Figure 2–11 shows another example of a three-member RAID 0 stripeset.
A major benefit of striping is that it balances the I/O load across all of the disk drives in
the storageset. This can increase the subsystem performance by eliminating the hot spots
(high localities of reference) that occur when frequently accessed data becomes
concentrated on a single disk drive.
Figure 2–11. A 3-member RAID 0 stripeset (example 2)
Keep the following points in mind as you plan your stripesets:
■ Reporting methods and size limitations prevent certain operating systems from
working with large stripesets.
■ A storageset should only contain disk drives of the same capacity. The controller limits
the effective capacity of each member to the capacity of the smallest member in the
storageset (base member size) when the storageset is initialized. Thus, if you combine
9 GB disk drives with 4 GB disk drives in the same storageset, you waste 5 GB of
capacity on each 9 GB member.
If you need high performance and high availability, consider using a RAIDset,
striped-mirrorset, or a host-based shadow of a stripeset.
Virtual disk
Block 0
Block 1
Block 2
Block 3
Block 4
Block 5
etc.
Disk 1
Block 0
Block 3
etc.
Disk 2
Block 1
Block 4
etc.
Disk 3
Block 2
Block 5
etc.
Operating
system
view
Actual
device
mappings
Stripeset
CXO4592B