How do I find which virtual machine is using this vdisk?
If you have the disk identifier, you can use this MySQL query to find which vm it belongs to:
select id,identifier,label,hostname,booted from virtual_machines where id in (select virtual_machine_id from disks where identifier='asdfasdfasdf12');
Be sure to replace 'asdfasdfasdf12' with the actual disk identifier.
If that returns nothing, then check to make sure this vdisk exists with:
lvscan | grep <<identifier>> for LVM or
onappstore list | grep -A10 <identifier>> for Integrated Storage
Those commands would need to be run on an HV with access to the appropriate datastore.