Specifications

4–18 Planning Storagesets
The relationship between the chunk size and the average request size determines if
striping maximizes the request rate or the data-transfer rates. 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.
Considerations for Planning a RAIDset
Keep these points in mind as you plan your RAIDsets:
■ A controller can support up to 20 storagesets, consisting of RAIDsets (refer to
Table 4–1).
■ Reporting methods and size limitations prevent certain operating systems from
working with large RAIDsets. 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 cache module is required for RAIDsets, but write-back cache need not be
enabled for the RAIDset to function properly.
■ Both cache modules must be the same size.
■ A RAIDset must include at least 3 disk drives, but no more than 14.
■ Evenly distribute the members across the device ports to balance load and
provide multiple paths as shown in Figure 4–4 on page 4–12.
■ 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, you will
waste 5 GB of capacity on each 9-GB member.
■ RAIDset units are set to WRITEBACK_CACHE by default which increases a
unit’s performance.
■ RAIDsets and mirrorsets on different ports to minimize risk in the event of a
single port bus failure.