VMware back up fails with “Failed to get changed disk areas: 12” (4042720)

VMware back up fails with “Failed to get changed disk areas: 12”

Netvault VMware backup fails when backing up vmdk disk files of  a Virtual Machine. The following is reported in the binary log:

VMWVIM :03544 686 0 82927 Failed to get changed disk areas: 12

VMWVIM :03544 29 0 82927 Soap error is Error caused by file /vmfs/volumes/4df1c8aa-5a729d29-4102-68b5996a652e/UKADTS2X/Helper-000006.vmdk

From the binary log Subtext:

Module/Thread Id Code Time Message

VMWUTIL :04576 6 0 135301 LoginToServer success=TRUE

VMWVIM :04576 686 0 135301 Failed to get changed disk areas: 12

VMWVIM :04576 29 0 135301 Soap error is Error caused by file /vmfs/volumes/4df1c8aa-5a729d29-4102-68b5996a652e/UKADSVR005/UKADSVR005-000001.vmdk

Trace shows change block tracking (CBT) has been enabled on this VM. This has been done manually or someone has run a CBT backup on this VM at some point.

From trace file vmw2148.log:

3 VMWBCKUP ??? 1656 186 0 141230447602 Computing disk areas to backup for VM disk '[SANiQiSCSI_Datastore03] UKADSVR005/UKADSVR005.vmdk'

3 VMWBCKUP ??? 1656 235 0 141230447602 CBT is enabled for VM disk

3 VMWVIM ??? 1656 659 0 141230447602 Datastore: 'SANiQiSCSI_Datastore03'

3 VMWVIM ??? 1656 660 0 141230447602 Folder: 'UKADSVR005'

3 VMWVIM ??? 1656 661 0 141230447602 File: 'UKADSVR005.vmdk'

3 VMWBCKUP ??? 1656 208 0 141230447602 Will use change id '*' to query for changed disk areas

6 VMWVIM ??? 1656 683 0 141230447602 Querying for changed disk areas from sector at offset 0 bytes

0 VMWVIM ??? 1656 686 0 141230494401 Failed to get changed disk areas: 12

0 VMWVIM ??? 1656 29 0 141230494401 Soap error is Error caused by file /vmfs/volumes/4df1c8aa-5a729d29-4102-68b5996a652e/UKADSVR005/UKADSVR005.vmdk

VMDK file is a disk file and the backup is trying to discover the blocks changed for a CBT backup because the VMX file has an entry setting the backup type to CBT. The netvault backup running does not have the CBT option selected for this backup and is trying to run either a file level backup. This conflict causes the backup failure.

WORKAROUND 1

Upgrade to vmware plugin 2.7

WORKAROUND 2

Modify the VMX file Disabling CBT for a Virtual Machine. See VMware plugin manual page 36 for procedure to do this at the URL below:

http://usdownloads.quest.com.edgesuite.net/Repository/support.quest.com/NetVault%20Backup/8.5.3/Documentation/Plugin%20for%20VMWare/NetVault_Backup_VMware_Plugin_Users_Guide_English.pdf

Or follow the proceedure below:

Procedure for Disabling CBT for a Virtual Machine

To disable CBT for any virtual machine, use the following steps:

1. Power off the virtual machine.

2. In the virtual machine's configuration (.vmx) file, edit the following entry and

set it to “False”:

ctkEnabled = "False"

3. In the .vmx file for each virtual disk, edit the following entry and set it to

“False”:

scsix:x.ctkEnabled = "False"

4. Create and delete a snapshot for the virtual machine in order to complete a

stun/unstun cycle.

Note: The .ctk files for the virtual machine will automatically be deleted when the

virtual machine is powered on the next time.

The backup option "Enable Changed Block Tracking for VM" is to provide a mechanism that will automatically enable CBT for all VMs in a backup set. Unticking it does not disable it. The error is from the VMware side and logged in Netvault as an error to ensure that the backup administrator can take appropriate action, either by resetting CBT or by fixing the cause of the failure in the VM. If using plugin 2.7 then resetting CBT can be done from the backup selection screen by right clicking the VM and selecting "reset change tracking" earlier version of the plugin do not have this feature available and would still need to perform the manual operations as described in the KB article - WORKAROUND 2. Additionally, In plugin version 2.7 as well, this error message will not fail the job but will fall back to backing up all blocks instead. Completing the job with warnings so that the administrator can go and check the reason for the problem. Please check the compatibility matrix before considering to upgrade.