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How to reset VMware Virtual Machine CBT


This document provides details for resetting CBT of a VMware VM.

Under certain circumstances CBT cannot be used please see:

In Veeam Backup & Replication v7 and older:

Cannot use CBT: Soap fault. A specified parameter was not correct. . deviceKeyDetail: '<InvalidArgumentFault xmlns="urn:internalvim25" xsi:type="InvalidArgument"><invalidProperty>deviceKey</invalidProperty></InvalidArgumentFault>', endpoint: ''

In Veeam Backup & Replication v8 and newer:

CBT data is invalid, failing over to legacy incremental backup. No action is required, next job run should start using CBT again. If CBT data remains invalid, follow KB1113 to perform CBT reset. Usual cause is power loss.

The following entries can be seen in the job log:

[timestamp] Info [AP] (Client) output: Soap fault. Error caused by file /vmfs/volumes/4b953b81-76b37f94-efef-0010185f132e/name/name.vmdkDetail: '', endpoint: ''\n
[timestamp] Info [AP] (Client) output: --tr:Failed to enumerate changed areas of the disk using CTK. Device key: [2000], size: [26843545600]. VM ref: [vm-xx]. Change ID: [*]\n

More information

Note: Resetting CBT is procedure which occurs within the VMware environment. If you require assistance with this procedure, please contact VMware Support.

When resetting CBT on a virtual machine, the next time the Backup or Replication job runs, the entirety of the disks on the Virtual Machine is read. It will not however create a new full (*.VBK) as blocks are compared to create a normal sized incremental.

Typically, a single job session with CBT warnings does not indicate a malfunction. VMware CBT will be automatically reset due to certain operations, such as Storage vMotion. Note that the presence of snapshots will prevent successful reset of CBT. For more information see

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