Veritas Storage Foundation Intelligent Storage Provisioning 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

21Understanding ISP
Frequently asked questions about ISP
The answer can be illustrated by an example. Suppose you create a storage
pool using the mirrored_volumes pool definition. This installs volume
templates that allow you to create mirrored volumes and volumes with
similar characteristics in the pool. If you attempted to create a striped
volume in the pool, the resulting volume is mirrored as well as striped.
However, you are not constrained from creating volumes with other
characteristics. You can use rules to bypass restrictions that are imposed by
higher-level abstractions like volume templates and capabilities.
Bear in mind that creating a storage pool from a storage pool definition
does not uniquely determine the capabilities of volumes that you create in
the pool. Only when you create a volume can you specify its capabilities and
ensure consistency between the volumes in a pool.
■ What does “prefabricated” mean as used in volume templates?
The term prefabricated implies that the characteristics of a volume are
implemented using hardware rather than software. For example,
PrefabricatedRaid5 implies the use of RAID-5 LUNs that have been set
up in an array’s hardware, rather than being implemented as a VxVM RAID-
5 volume.
■ Can I use both hardware and software RAID volumes in a storage pool?
A storage pool is usually configured either for prefabricated RAID devices
or for VxVM volumes that are created in software. This provides
consistency in performance and failure tolerance within the pool. If you add
both hardware and software RAID templates to a pool, ISP allocates
templates that are appropriate to the capabilities of the volumes that you
specify.
■ How does ISP discover LUN hardware characteristics?
ISP relies on the Veritas Array Integration Layer (VAIL) to provide detailed
information on LUN characteristics via array-specific modules.
■ How do I restrict allocation to storage from certain vendors, for example EMC
BCV or Hitachi?
By default, ISP uses LUNs with similar characteristics for allocating
storage. If insufficient storage is available, it relaxes this constraint. You
can make the constraint mandatory by specifying the capability
ArrayProductId when creating a volume. This forces ISP to allocate
storage on LUNS that share the same product identifier. Alternatively, you
can use the capability ConfineToSimilarStorage. This makes ISP use
LUNs from the same vendor, but allows the product identifiers of these
LUNs to differ.