Specifications

4–10 Planning Storagesets
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 let the controller set it automatically. See “Chunk Size,” page 4–43, for
information about setting the chunk size.
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’s performance by eliminating the
hot spots, or high localities of reference, that occur when frequently-accessed data
becomes concentrated on a single disk drive.
Considerations for Planning a Stripeset
Keep the following points in mind as you plan your stripesets:
■ A controller can support up to 45 storagesets, consisting of stripesets, mirrorsets
and RAIDsets (refer to Table 4–1).
■ Reporting methods and size limitations prevent certain operating systems from
working with large stripesets. See the HSG80 Array Controller ACS Version 8.X
Release Notes or the Quick Setup Guide that came with your platform kit for
details about these restrictions.
■ A storageset should only contain disk drives of the same capacity. The controller
limits the capacity of each member to the capacity of the smallest member in the
storageset when the storageset is initialized (the base member size). Thus, if you
combine 9 GB disk drives with 4 GB disk drives in the same storageset, the 4 GB
disk drive will be the base member size, and you will waste 5 GB of capacity on
each 9 GB member.
■ Striping does not protect against data loss. In fact, because the failure of one
member is equivalent to the failure of the entire stripeset, the likelihood of losing
data is higher for a stripeset than for a single disk drive.