One or more virtual servers is/are not committing snapshot changes
– The Snapshot Manager shows no snapshots but there are delta files present.
– One or more sets of -00000X.vmdk and -00000X-delta.vmdk files are in the directory with the virtual disk.
– The .vmx file points to one of the -00000X.vmdk files, usually the highest numbered file, indicating that the snapshot file is in use.
Creating a new snapshot and choosing the “Delete All” option fails with the same error message:
“The virtual disk is either corrupted or not a supported file format”
The server is therefore running off snapshot images.
Schedule maintenance downtime out of hours. Shut down the VM(s) affected. Create a new snapshot (not quiesced; do not tick either of the options) and then “Delete All” through the Snapshot Manager. This will take a few hours depending on the amount of data to be committed. After a successful completion, you will see your VM drives are not longer operating off snapshots; if in the rare event they are, edit the .vmx file paths and re-run the process). You may need to delete any snapshot file remnants through the Datastore Browser (any you can’t delete, move into a new sub-folder and then delete the sub-folder).
The issue most likely arises when backups are taken. The long-term solution is to increase the amount of RAM assigned to your vCenter host as the connection through to your backup software is temporarily dropping.