[PVE-User] Query disk usage

[Marcus]

To make this work you have to activate "discard" option in proxmox per 
harddisk, set bus to "scsi" and use virtio-scsci as controller.
I use XFS only, but ext4 provides discard also.
> Mandi! Marcus
>    In chel di` si favelave...
>
>> Yes, that's possible. Use fstrim or mount the volume with "discard" as
> 	root at brucaliffo:~# fstrim -v /var
> 	fstrim: /var: the discard operation is not supported
>
> /var is an ext4 filesystem, debian jessie.
>
> Why?
>