Snapshot Consolidation in VMware ESXi 5.5 fails

Symptoms

  • Cannot perform snapshot consolidation in VMware ESXi 5.5 and ESXi 6.0.x.
  • Performing a snapshot consolidation in ESXi 5.5 fails.
  • When attempting to consolidate snapshots using the vSphere Client, you see the error:
    • maximum consolidate retries was exceeded for scsix:x
    • Consolidate Disks message: The virtual machine has exceeded the maximum downtime of 12 seconds for disk consolidation

Cause

This issue occurs because ESXi 5.5 introduced a different behavior to prevent the virtual machine from being stunned for an extended period of time.
This message is reported if the virtual machine is powered on and the asynchronous consolidation fails after 10 iterations. An additional iteration is performed if the estimated stun time is over 12 seconds.This occurs when the virtual machine generates data faster than the consolidated rate.
In comparison with previous version of ESXi, if the asynchronous consolidation fails after 10 iterations, the virtual machine is stunned until the remaining data is consolidated. For more information, see Virtual machines become unresponsive for over 30 minutes when removing a snapshot (2039754).

Resolution

To resolve this issue, turn off the snapshots consolidation enhancement in ESXi 5.5 and ESXi 6.0.x, so that it works like earlier versions of ESX/ESXi. This can be done by setting the snapshot.asyncConsolidate.forceSync to TRUE.
Note: If the parameter is set to true, the virtual machine is stunned for long time to perform the snapshot consolidation, and it may not respond to ping during the consolidation.

To set the parameter snapshot.asyncConsolidate.forceSync to TRUE using the vSphere client:

  1. Shut down the virtual machine.
  2. Right-click the virtual machine and click Edit settings.
  3. Click the Options tab.
  4. Under Advanced, right-click General
  5. Click Configuration Parameters, then click Add Row.
  6. In the left pane, add this parameter:
    snapshot.asyncConsolidate.forceSync
  7. In the right pane, add this value:
    TRUE
  8. Click OK to save your change, and power on the virtual machine.

To set the parameter snapshot.asyncConsolidate.forceSync to TRUE without shutting down the virtual machine, run this Powercli command:
get-vm virtual_machine_name | New-AdvancedSetting -Name snapshot.asyncConsolidate.forceSync -Value TRUE -Confirm:$False
Note
: To work around this issue, when under heavy IO load, you can alternatively retry snapshot consolidation at a time when the virtual machine is issuing less IO.

Additional Information

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You can increase the time limit on the snapshots consolidation by changing the configuration parameters.

 

To change the Configuration parameter to increase the time limit on the snapshots consolidation:

  1. Shut down the virtual machine.
  2. Right-click the virtual machine and click Edit Settings.
  3. Click the Options tab.
  4. Under Advanced, click General.
  5. Click Configuration Parameters and add snapshot.maxConsolidateTime = 30.

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