Unitrends offers VMware VADP-level backup protection in its backup appliances beginning with release 5.  One of the primary objections to using this for some Windows clients has been what’s known as the application-level quiescing problem – the fact that applications running within a Windows GOS (Guest Operating System) such as SQL or Exchange would not produce crash-consistent backups – in plain speak, when you went to recover you’d have to perform integrity tests to attempt to recover partial data for these applications.

With VMware 4.1, this is now supported.  The tables and text below describe this:

Guest Operating System Quiescing Type Used
  • Windows XP 32-Bit
  • Windows 2000 32-Bit
  • Windows Vista 32-Bit/64-Bit
  • Windows 7 32-Bit/64-Bit
File system-consistent quiescing
  • Windows 2003 32-Bit/64-Bit
Application-consistent quiescing
(Pre VMware ESX 4.1 Hosts)

  • Windows 2008 32-Bit/64-Bit
  • Windows 2008 R2
File system-consistent quiescing
(VMware ESX 4.1 and Later Hosts)

  • Windows 2008 32-Bit/64-Bit
  • Windows 2008 R2
Application-consistent quiescing.For application consistent quiescing to be available, three conditions must be met:

  • The UUID attribute must be enabled. This is enabled by default on virtual machines created on ESX 4.1 hosts. For virtual machines created on other hosts, see below
  • The virtual machine must use only SCSI disks.  For example, application-consistent quiescing is not supported for virtual machines with IDE disks. There must as many free SCSI slots in the virtual machine as the number of disks. For example, if there are 8 SCSI disks on SCSI adapter 1, there are not enough SCSI slots free to perform application quiescing.
  • The virtual machine must not use dynamic disks.
Other Guest Operating Systems Crash-consistent quiescing


Enable Windows 2008 Virtual Machine Application Consistent Quiescing for VMware 4.0

Windows 2008 virtual machines created on ESX/ESXi 4.0 hosts can be enabled for application consistent quiescing on ESX/ESXi 4.1 hosts by enabling the disk UUID attribute.


  1. Start the vSphere Client, and log in to a vCenter Server.
  2. Select Virtual Machines and Templates and click the Virtual Machines tab.
  3. Right-click the Windows 2008 virtual machine for which you are enabling the disk UUID attribute, and select Power > Power Off.  The virtual machine powers off.
  4. Right-click the virtual machine, and click Edit Settings.
  5. Click the Options tab, and select the General entry in the settings column.
  6. Click Configuration Parameters… The Configuration Parameters window appears.
  7. Click Add Row.
  8. In the Name column, enter disk.EnableUUID.
  9. In the Value column, enter TRUE.
  10. Click OK and click Save.
  11. Power on the virtual machine.  

 Application consistent quiescing is available for this virtual machine now that the UUID property has been enabled.