Volume Shadow Copy Service (VSS) for virtual machines

This option defines whether quiesced snapshots of virtual machines are taken. To take a quiesced snapshot, the backup software applies VSS inside a virtual machine by using VMware Tools, Hyper-V Integration Services, Virtuozzo Guest Tools, Red Hat Virtualization Guest Tools, or QEMU Guest Tools, respectively.

For Red Hat Virtualization (oVirt) virtual machines, we recommend that you install QEMU Guest Tools instead of Red Hat Virtualization Guest Tools. Some versions of Red Hat Virtualization Guest Tools do not support application-consistent snapshots.

The preset is: Enabled.

If this option is enabled, transactions of all VSS-aware applications running in a virtual machine are completed before taking snapshot. If a quiesced snapshot fails after the number of re-attempts specified in the "Error handling" option, and application backup is disabled, a non-quiesced snapshot is taken. If application backup is enabled, the backup fails.

Enabling the Volume Shadow Copy Service (VSS) for virtual machines option also triggers the pre‐freeze and post‐thaw scripts that you might have on backed-up the virtual machine. For more information on these scripts, refer to Running pre‐freeze and post‐thaw scripts automatically.

If this option is disabled, a non-quiesced snapshot is taken. The virtual machine will be backed up in a crash-consistent state.

This option does not affect Scale Computing HC3 virtual machines. For them, quiescing depends on whether Scale Tools are installed on the virtual machine.