HP Veritas Volume Manager 5.0 -UX 11i v3 manual Implementing off-host online backup

Configuring off-host processing

Implementing off-host processing solutions

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■Implementing decision support

These applications use the Persistent FastResync feature of VxVM in conjunction with linked break-off snapshots.

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.

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. 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.

To back up a volume in a private disk group

1Use the following command on the primary host to see if the volume is associated with a version 20 data change object (DCO) and DCO volume that allow instant snapshots and Persistent FastResync to be used with the volume:

#vxprint -g volumedg -F%instant volume

This command returns on if the volume can be used for instant snapshot operations; otherwise, it returns off.