[PVE-User] Query disk usage

[Yannis Milios]

>> So if you allocate 100GB to a vm disk, and write a 99GB at some time,
>> then delete 98GB, the vm-disk will still report 99GB of allocated space
>> AFAIK

Is it possible to reclaim this space by using virtio scsi as a virtual
storage controller on the vm and then enabling discard option?
Do we need to run upper layer tools like sdelete (windows) and fstrim
(linux) to reclaim disk space?