>>> You want file listing on each VM folder on first datastore?

Yes, that's what I'm thinking of. This will help to find out how much disk space will be required to consolidate the snapshots, and to find out whether there's an option to free up enough disk space by e.g. temporarily shutting down other VMs.

If that doesn't help, we can clone the Ubuntu VMs virtual disk to the second datastore, and in the same step consolidate all snapshots.

André