Veritas Storage Foundation Intelligent Storage Provisioning 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

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.
■ When I create a volume, ISP uses space on the same disks unless I choose other
disks from the storage pool manually. Why doesn’t ISP automatically spread
the volumes across the other disks in the storage pool to enhance I/O
performance?
ISP is tuned to use as few disks as possible. In any case, I/O performance
depends on many factors such as the way storage is connected to the system,
the inherent capabilities of the storage, how volumes are configured and how
23Understanding ISP
Frequently asked questions about ISP