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PHDVB User Guide > PHD Virtual Backup Overview > Application Aware Backups

Application Aware Backups

With version 6.0, PHD Virtual Backup introduced the ability to create application-consistent backups, including the ability to properly quiesce applications before backup and to perform required post-backup processing tasks, such as log truncation for Microsoft Exchange. PHD Virtual Backup's application aware functionality is enabled by a small guest application, the PHD Guest Tools (for installation instructions, see Installing PHD Guest Tools).

PHD Virtual Backup takes advantage of Microsoft's Volume Shadow Copy Service (VSS) to perform quiesce for any VSS-aware applications running on the virtual machine to ensure an application-consistent backup is created. In addition, to avoid running out of storage space on your VM, a log truncation option is available for Microsoft Exchange. Along with the application aware functionality provided when you installed the PHD Guest Tools, you can supply your own scripts or commands to perform additional processing for any VSS-aware applications.

Tip:    Application aware processing and custom script options are enabled when you create the backup job, using the VM Processing Options step of the Backup wizard. See Using the Backup Wizard for details.

Figure B - 8. Backup wizard - VM Processing Options step.

PHD Virtual Backup uses scripts to perform the application aware processing on the guest VM. By supplying your own scripts and commands, you can provide your own application aware processing for other database applications, for example:

To use custom scripts or commands, copy them to the appropriate PHD Guest Tools sub-directory on the guest VM. For details, see Using Custom Scripts.

The Quiesce Process

With PHD Guest Tools installed, PHD Virtual Backup can create transactionally-consistent backups for VMs running applications that are VSS-aware.

When an application aware backup is started, PHD Guest Tools initiates the quiesce process and an application-consistent VSS snapshot is created on the VM. The backup process continues and writes the data to the backup store while this snapshot exists on disk. When the backup process completes, post-backup processing options are executed and the VSS snapshot is removed from the guest virtual machine.

When the backup is recovered, you can revert to an application-consistent state using the stored VSS snapshot. A README file is included on the restored VM that includes the commands required for viewing and reverting to the stored VSS snapshots. This file includes custom commands that can be copied and pasted to a command prompt to perform the available functions. A separate custom command is included in the README file for each disk of the VM. For additional details on restoring application consistent backups, see Recovering Application Aware Backups.

If you enabled quiesce during the backup wizard, but the PHD Guest Tools are not installed on a guest VM, VMware tools will be used to initiate the quiesce process. In this case, no VSS snapshot is stored with the backup.

In addition to initiating the quiesce process, enabling the quiesce option will run any custom scripts that you've included in the pre-snapshot and post-snapshot directories. For additional details on using custom scripts, see Using Custom Scripts.

Note:    Windows Powershell v1.0 or later is required to perform quiesce on guest VMs.

Log Truncation - Microsoft Exchange

If you are running Microsoft Exchange in your environment, you have the option to perform log truncation to ensure logs don't cause you to run out of storage space. Log truncation requires the PHD Guest Tools installed on the MS Exchange server virtual machine. When you create the backup job, at the VM Processing Options step you can enable log truncation and select to truncate logs after a successful backup or always after the backup process is completed.

Note:    Log truncation is supported for Microsoft Exchange running on Windows 2003 Server 64 bit SP2 and later and Windows Server 2008 R2 SP1 and later.

Caution:   If the application aware backup job is interrupted, the PHD Guest Tools service may continue to run on the guest VM. In this scenario, you will need to manually stop the service to instruct Exchange to cease writing to logs. Although the service will be stopped automatically the next time the backup job runs, you run the risk of running out of free space while Exchange continues to writes to log files.

Log truncation can be performed for other applications using your own custom scripts or commands. For details, see Using Custom Scripts.

Log Truncation - Microsoft SQL Server

To perform log truncation for Microsoft SQL Server, you can use custom scripts to send the commands required to your SQL Server database. Example scripts are included with the PHD Virtual Backup installation package, along with instructions for modifying those scripts, to enable log truncation for SQL Server.

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