In ESX 3.5, when trying to create a new snapshot, the following error is reported in the VI Client:

An invalid snapshot configuration was detected


Also, when reading the Virtual Machine log file (vmware.log) located in the same location as the VM, you may find references to delta files such as "vm_name-000001.vmdk", but when browsing the datastore, the delta file does not exists. Also, when running vmware-cmd hassnapshot,  "hassnapshot ()= " is returned, which means that the VM has no snapshots in place.

If this is truly the case, why is "An invalid snapshot configuration was detected" returned when trying to create a new snapshot?

VMware records snapshot information about the current VM in a .vmsd file. This file is located with the rest of the virtual machine configuration and VMDK files on the datastore. The file is normally called .vmsd. This file will contain information, even if your VM has no snapshots in place.

It is possible that in some cases, ESX fails to properly clean up after previous snapshots were removed. The information for previous snapshots may still be recorded in the .vmsd file. The file may indicate that you still have snapshots in pace, although all previous snapshots were removed and the dalta files have been merged. When you then try to create a snapshot, the .vmsd file will inform the ESX host that there is a delta file in place and that it has to create a second or third delta file. When the ESX host interigates the VMFS file system, it's unable to find the snapshot delta files specified in the .vmsd file and therefore errors with "an invalid snapshot configuration was detected."

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@martinclarkson I know. That kinda sucks though. All good things must eventually come to an end.
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