HP StorageWorks HSG80 ACS Solution Software V8.8 for IBM AIX Installation and Configuration Guide (AA-RV1HA-TE, March 2005)

Planning Storage Configurations
81HSG80 ACS Solution Software V8.8 for IBM AIX Installation and Configuration Guide
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 93, for information about
setting the chunk size). Figure 25 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 25: Three-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