VERITAS Storage Foundation 4.1 Intelligent Storage Provisioning Administrator's Guide

Chapter 1, Understanding ISP

Frequently Asked Questions About ISP

◆ 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 use 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: the way storage is connected to the system, the inherent capabilities of the storage,

how volumes are configured and how they share storage, the type of I/O requests made by

applications, and the amount of I/O from/to each volume. For example, allocating two volumes

to a single disk array that has a large cache would probably provide better overall I/O

performance than placing one volume on the disk array and the other on a JBOD. If necessary,

you can configure smaller storage pools in separate disk groups to restrict the allocation of

storage. Alternatively, you can explicitly specify the storage that can or cannot be allocated to

a volume.