"Consolidate Helper-0" Snapshots are left behind and can not be deleted when running AVVI enabled backups

Problem

There is a "consolidate helper-0" snapshot on vCenter Snapshot Manager after a backup using AVVI (Agent for VMware Virtual Infrastructure). 

When trying to manually delete snapshot from snapshot manager in vCenter, receive error:

  -  Unable to access file <unspecified filename> since it is locked

Error Message

vCenter Events & Tasks tab:

Unable to access file <unspecified filename> since it is locked

Cause

The “Consolidated Helper-0” snapshot is automatically created by the ESX host during snapshot management process, like a delete SYMC snapshot from Backup Exec.   

When the last snapshot is being removed from the virtual machine, the ESX host creates a "Consolidate Helper-0" snapshot to host the data writes while the actual snapshot is being removed. After that is done, the actual "consolidate helper" snapshot is injected (committed) to the main VMDK by ESX.  In order to successfully commit the last helper snapshot, the virtual machine I/O must be completely frozen, so the commit can only take place if both of these conditions are true:

   - Helper snapshot size is less than 16MB (which is minimal snapshot size in VMware)

   - There is very little write I/O going on the VM at the given moment

The “Consolidated Helper-0” snapshot will continue to show in the vCenter Snapshot Manager until it finds until the above conditions are met to commit the snapshot to the VMDK.

 

This issue can be a confirmed VMware I/O issue by completing the following:

1. Restart the virtual machine so to commit the “Consolidated Helper-0) snapshot
2. Create a file quiesce snapshot through vCenter/vSphere Snapshot Manager (should complete successfully)
3. Delete the snapshot from vCenter/vSphere Snapshot Manager
   1. The file system quiesce snapshot should be deleted, but a "Consolidate Helper-0" snapshot remains
   2. The following error will show in vCenter/vSphere “Unable to access file <unspecified filename> since it is locked”

Solution

NOTE:  As the cause of the issue is outside of the Backup Exec program, the following solutions are simply recommendations from Symantec Backup Exec support.  Please contact VMware Support for further assistance on this VMware related issue.

 Fix: Adjust your virtual environment to resolve the high I/O

Workaround: Restart the virtual machine to allow the quiesce time to commit the snapshot.

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