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Title
Failed to determine disk areas to backup for VM disk -
Description
NetVault VMware Plugin Backup fails with the following error:
"Failed to determine disk areas to backup for VM disk"
The sub context reveals that it is not possible to locate the changed block.
VMWUTIL :03188 6 0 91237 LoginToServer success=TRUE
VMWVIM :03188 686 0 91238 Failed to get changed disk areas: 12 -
Cause
VMware have identified some cases, such as a power failure or hard shutdown while virtual machines are powered on, where CBT might reset and lose track of incremental changes. Likewise offline Storage vMotion, but not online Storage vMotion, could reset but not disable CBT.
More information can be found in VMware Knowledgebase article 1020128 "Changed Block Tracking (CBT) on virtual machines"
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Resolution
Resetting CBT on a virtual machine
During Incremental or Differential backups, if the plug-in is unable to determine the changed disk sectors for a virtual machine, it reports an error (“Failed to determine disk areas to backup”) and backs up the entire disk. When this occurs, use the following procedure to reset change tracking for the virtual machine. Before proceeding, delete any existing snapshots of the target virtual machine.
To reset CBT on a virtual machine
1 Start the Backup Job Wizard, and click Create New next to the Selections list.
2 Open the NetVault Backup Client on which plug-in is installed, and then open VMware Plugin.
3 Open the ESX/ESXi or vCenter Server and the other applicable container nodes (that is, the vCenter, Datacenter, Cluster, Resource Pool, vApp, and ESX/ESXi Server nodes) to display the target virtual machine.
4 Select the target virtual machine, and in the Actions list, click Reset Change Tracking. This option is available to only those virtual machines on which CBT is currently enabled.
5 After the virtual machine is reconfigured, a message is displayed. Click OK to close the dialog box.
Important notes
• When CBT is being reset, no snapshots should exist for the virtual machine. Otherwise, the reset operation will fail.
• If CBT is reset for a virtual machine that is powered off, we recommend that you power on the virtual machine before running a CBT-enabled backup for that virtual machine. If you perform a CBT-enabled backup in the powered off state, the backup may report the following error and fail: Log message – Failed to determine disk areas to backup. Log context – A specified parameter was not correct. deviceKey.
• After CBT is reset for a virtual machine, the next Incremental Backup backs up all blocks for that virtual machine. Subsequent Incremental Backups only back up the disk sectors that have changed.
• If an error message is displayed while CBT is being reset, check the “Recent Tasks” window on the vSphere Client for any messages that explain why the request failed.