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

Note: A volume snapshot represents the data that exists in a volume at a given

point in time. As such, VxVM does not have any knowledge of data that is cached

by the overlying file system, or by applications such as databases that have files

open in the file system. If the fsgen volume usage type is set on a volume that

contains a Veritas File System (VxFS), intent logging of the file system metadata

ensures the internal consistency of the file system that is backed up. For other

file system types, depending on the intent logging capabilities of the file system,

there may potentially be inconsistencies between in-memory data and the data

in the snapshot image.

For databases, a suitable mechanism must additionally be used to ensure the

integrity of tablespace data when the volume snapshot is taken. The facility to

temporarily suspend file system I/O is provided by most modern database software.

For ordinary files in a file system, which may be open to a wide variety of different

applications, there may be no way to ensure the complete integrity of the file data

other than by shutting down the applications and temporarily unmounting the

file system. In many cases, it may only be important to ensure the integrity of file

data that is not in active use at the time that you take the snapshot.

The following sections describe how you can apply off-host processing to

implement regular online backup of a volume in a private disk group, and to set

up a replica of a production database for decision support. Two applications are

outlined:

■ Implementing off-host online backup

■ Implementing decision support

These applications use the Persistent FastResync feature of VxVM in conjunction

with linked break-off snapshots.

Implementing off-host online backup

This section describes a procedure for implementing off-host online backup for

a volume in a private disk group. The intention is to present an outline of how to

set up a regular backup cycle by combining the Persistent FastResync and linked

break-off snapshot features of VxVM. It is beyond the scope of this guide to

describe how to configure a database to use this procedure, or how to perform the

backup itself.

Off-host processing solutions

Implementing off-host processing solutions