Dell EMC Avamar for VMware 19.7 User Guide

Image backup virtual machine quiescing

Image backup does not provide any additional virtual machine quiescing capabilities other than those features that are provided by VMware vStorage API for Data Protection (VADP).

Before performing an image backup, three levels of virtual machine quiescing are possible:

• Crash-consistent quiescing
• File system-consistent quiescing
• Application-consistent quiescing

Crash-consistent quiescing is the least desirable level of quiescing because the virtual disk image being backed up is consistent with what would occur by interrupting power to a physical computer. File system writes might or might not be in progress when power is interrupted. Because of this issue, there is always a chance of some data loss.

File system-consistent quiescing is more desirable because the virtual machine is allowed to complete any file system writes before the disk is backed up. This level of quiescing is only available on Windows virtual machines capable of providing Windows Volume Snapshot Service (VSS) services, and that are running VMware Tools.

Application-consistent quiescing is the most desirable level of quiescing. In addition to the advantages provided by file system-consistent quiescing, applications are notified that a backup has occurred so that they can clear their transaction logs.

Application-consistent quiescing is only available on Windows Vista/2008 and later virtual machines that are running VMware Tools.