No Protection Against Deleting a Disk Backing File That Is Also Used by Another Powered-Off Virtual Machine

In VirtualCenter 1.x, removing a disk from a virtual machine unconditionally left the disk file on the datastore. VirtualCenter 2.0 adds the option to delete the backing file when you remove a disk from a virtual machine. If you choose to delete the file but it is in use by a powered-on virtual machine, an error occurs and the disk is not deleted from the datastore. But if the only other users of the disk file are not currently powered on, the deletion succeeds and those other virtual machines no longer function.

This problem is most likely to come up with raw disk mappings (RDM) where the LUN is intended to be used by only one virtual machine at a time, but multiple virtual machines use it at different times. In the RDM case, it is also possible to recover from this problem.

If the deleted disk is an RDM and the target LUN hasn't been destroyed in the meantime, simply creating a new RDM for the same LUN allows the other virtual machines to function again. This workaround doesn't work for a regular virtual disk. The best protection is to be careful when choosing to delete the disk completely rather than remove it from the virtual machine and leave the backing file on the datastore.