VERITAS Storage Foundation 4.1 Intelligent Storage Provisioning Administrator's Guide

Frequently Asked Questions About ISP
26 VERITAS Storage Foundation ISP Administrator’s Guide
Frequently Asked Questions About ISP
◆ What is the relationship between a storage pool and a volume template?
Storage pools contain disks, VxVM objects such as volumes, and a set of volume templates. A
storage pool is defined by the volume templates that it contains. The ISP Configuration
Database contains a number of storage pool definitions that you can use to create a storage
pool object in VxVM. Each definition contains a list of volume templates and the default
policy settings for the pool definition. When you create a storage pool object in a disk group
from a storage pool definition, these volume templates and policies also get installed.
◆ When do I need to specify a template set?
A storage pool contains volume templates that define its characteristics. A template set is
simply a collection of related volume templates that you can associate with a storage pool.
◆ When do I need to specify a storage pool set?
A disk group that you want to use with ISP must be configured to contain one data storage
pool, and optionally one or more clone storage pools. You can use a storage pool set definition
to organize a disk group so that it contains data and clone storage pools with well-defined
characteristics.
◆ If I create a storage pool using a storage pool definition, can I later create a volume in that
pool using a volume template other than those that are associated with the pool?
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.