VSS for Exchange Database iDataAgents

Overview

When using VSS, write operations on the data being backed up can continue while these open files are copied and backed up, eliminating locked file conditions.

VSS can be enabled for backups of local volumes in both clustered and non-clustered environments. If the operating system fails to create a shadow copy of the data a traditional backup of the data will be performed, and a corresponding message will appear in the Event Viewer.

During a VSS backup, the free space needed on a volume for the shadow copy is related to the duration of the backup and the amount changes being made to the data objects (files, databases) that are being backed up. VSS snapshots capture and copy disk blocks that are being changed by other processes while the backup for a particular object is running. If the backup runs longer, or there is a lot of disk activity (files or databases being changed), this would cause VSS to copy more data blocks and therefore, use more disk space.

VSS Software Providers

Microsoft Volume Shadow Service is the default, and only supported VSS software provider. The VSS software provider takes a snapshot of the source volume, database or file, which is then used to create backups or QR Volumes (when used with the Quick Recovery Agent).

Using VSS with Exchange 2003/2007

VSS can be enabled for backups of local NTFS volumes. If selected, the following will automatically occur:

All previously scheduled incremental, differential and traditional full backups are converted to VSS enabled full backups.
A consistency check of the database integrity will be performed by the system prior to backing up the data, and if the integrity check fails then the backup will fail.

Before selecting the Use VSS option with Exchange, you should review the VSS-related items in this agent's Restore Considerations.

When a new Mailbox Store or Public Folder Store is added to an existing storage group, you must always perform a full backup before running incremental/differential backups.

After restoring from a VSS-enabled backup, you must manually select a Full backup to be run from the Backup Options dialog because the system will not automatically convert a pre-selected incremental or differential backup to a full backup in this scenario.

Advantages of using VSS Enabled Backups with Exchange 2003/2007

Using VSS enabled backups to secure Exchange data offers the following advantages:

Produces a backup of an entire Storage Group that reflects the state of the Storage Group at the instant the backup started, even if the individual store data changes while the backup is in progress. All the data in the backup is internally consistent and reflects the state of the volume at a single point-in-time.
VSS enabled backups will notify Exchange 2003/2007 that a backup is about to occur. Exchange can then prepare for the backup by flushing caches, log files and cleaning up on-disk structures.
Incremental, Differential and Full backup types are supported for VSS-enabled backups with the Exchange Database iDataAgent.
VSS can also be used in conjunction with the Exchange 2007 Database iDataAgent to perform shadow copy backups of a replica database and logs in a Cluster Continuous Replication (CCR) configuration. For more information, see Cluster Continuous Replication (CCR) Backups.
Out-of-Place restores from VSS-enabled backups for the Exchange 2007 Database iDataAgent allow the database stores to be restored to a different storage group (including Recovery Storage Groups) on the same Exchange Server, or to a different Exchange Server within the same Exchange organization, or to a physically different location on disk (i.e., non-Exchange location) with a choice of whether or not to replay the logs. For step-by-step instructions, see Restore Out-of-Place or Cross-Application.
A throttling option is available for the consistency check to establish periodic pause points in the process, in order to more efficiently utilize Exchange system resources during the consistency check process. For more information, see Configuring Consistency Check Throttling.

Configuration

The following must be done before using VSS.

Enable VSS Backups of an Exchange Database