Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

About VxVM volume sets
Volume sets allow several volumes to be represented by a single logical object.
Volume sets cannot be empty. All I/O from and to the underlying volumes is
directed via the I/O interfaces of the volume set. The volume set feature supports
the multi-volume enhancement to Veritas File System (VxFS). This feature allows
file systems to make best use of the different performance and availability
characteristics of the underlying volumes. For example, file system metadata
could be stored on volumes with higher redundancy, and user data on volumes
with better performance.
About volume tags
You make a VxVM volume part of a placement class by associating a volume tag
with it. For file placement purposes, VxFS treats all of the volumes in a placement
class as equivalent, and balances space allocation across them. A volume may
have more than one tag associated with it. If a volume has multiple tags, the
volume belongs to multiple placement classes and is subject to allocation and
relocation policies that relate to any of the placement classes. Multiple tagging
should be used carefully.
A placement class is a Dynamic Storage Tiering attribute of a given volume in a
volume set of a multi-volume file system. This attribute is a character string, and
is known as a volume tag.
About Dynamic Storage Tiering policies
Dynamic Storage Tiering allows administrators of multi-volume VxFS file systems
to manage the placement of files on individual volumes in a volume set by defining
placement policies that control both initial file location and the circumstances
under which existing files are relocated. These placement policies cause the files
to which they apply to be created and extended on specific subsets of a file system's
volume set, known as placement classes. The files are relocated to volumes in
other placement classes when they meet the specified naming, timing, access rate,
and storage capacity-related conditions.
Database Dynamic Storage Tiering in a High Availability (HA)
environment
Veritas Cluster Server does not provide a bundled agent for volume sets. If issues
arise with volumes or volume sets, the issues can only be detected at the DiskGroup
and Mount resource levels.
The DiskGroup agent brings online, takes offline, and monitors a Veritas Volume
Manager (VxVM) disk group. This agent uses VxVM commands. When the value
185Using Database Dynamic Storage Tiering
About Database Dynamic Storage Tiering