This is a common issue on raidz based pools. Assuming 4k sectors (ashift=12) and zvol with 8K volblocksize, each 8K (2-sector) block uses a single sector (4k) of parity. So 15TB of 8KB blocks (default volblocksize=8k) takes up at least 22.5TB space on disk (including parity). You will use less parity by increasing the volblock size (e.g. volblocksize=32k, or the default recordsize=128k for filesystems) in exchange of a possible lower performance. Another solution would be using a pool of striped mirrors (RAID10). This problem does not exist in such pools (as there are no parity blocks used).
On Mon, 5 Apr 2021 at 09:23, Konold, Martin <[email protected]> wrote: > > Hi, > > I set up a single VM which currently used 15TB of data. > /dev/sdb is technically a ZFS volume on the Proxmox Host. > > [root@vm ~]# df -h /data > Filesystem Size Used Avail Use% Mounted on > /dev/sdb 40T 15T 25T 37% /data > [root@vm ~]# du -s /data/ > 14874345100 /data/ > > [root@host /]# zfs list zfs01/PVE-BE/vm-1-disk-1 > NAME USED AVAIL REFER MOUNTPOINT > zfs01/PVE-BE/vm-1-disk-1 31.5T 5.82T 31.5T - > > Why is the usage on the host about twice as large as within the vm? > (Yes, I have given fstrim and discard a try). > > -- > Regards > ppa. Martin Konold > > -- > Martin Konold - Prokurist, CTO > KONSEC GmbH - make things real > Amtsgericht Stuttgart, HRB 23690 > Geschäftsführer: Andreas Mack > Im Köller 3, 70794 Filderstadt, Germany > <https://www.google.com/maps/search/Im+K%C3%B6ller+3,+70794+Filderstadt,+Germany?entry=gmail&source=g> > > _______________________________________________ > pve-user mailing list > [email protected] > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user > _______________________________________________ pve-user mailing list [email protected] https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-user
