[PVE-User] zfs 0.7 no discard

Mark Adams mark at openvs.co.uk
Tue Jul 9 22:24:39 CEST 2019


Ah right! thanks for that info, I had assumed it would use fstrim. Looks
like zpool trim is what I need to be running once upgraded.

Cheers,
Mark

On Tue, 9 Jul 2019 at 21:19, Gianni Milo <gianni.milo22 at gmail.com> wrote:

> On that case, I would upgrade the VM to zfs 0.8, leaving the host on zfs
> 0.7 with compression enabled.
> Then I would run zfs trim command inside the VM and see if the space is
> reclaimed back on the host.
>
> Note: fstrim command only works on specific filesystems, not in zfs.
>
> Gianni
>
>
>
> On Tue, 9 Jul 2019 at 21:01, Mark Adams <mark at openvs.co.uk> wrote:
>
> > Hi GIanni,
> >
> > Thanks for your response, what I forgot to mention is I am also using zfs
> > inside of the VM, which I think is the main problem - I need it to be 0.8
> > to actually send the discard/trim command to the underlying zfs... what
> I'm
> > not clear on is if I need both to be 0.8.
> >
> > Also, I assume this can be done retrospectively ? so if I upgrade then I
> > can run fstrim and it will clear the space in the host...? Maybe that
> > question is better posed to the zfsonlinux list though...
> >
> > Cheers,
> > Mark
> >
> > On Tue, 9 Jul 2019 at 20:53, Gianni Milo <gianni.milo22 at gmail.com>
> wrote:
> >
> > > Haven't moved to zfs 0.8 but you could have similar results by enabling
> > > compression on zfs and by periodically executing fstrim (linux) or
> > sdelete
> > > (windows) inside VMs to reclaim unused space ?
> > >
> > > On Linux VMs, adding "discard" in fstab mount options (ext4) may have
> > > similar results as when executing fstrim.
> > >
> > > On Windows 10/2012+ VMs, defrag command can be used to perform free
> space
> > > consolidation.
> > >
> > > Make sure you enable "discard" option on the VM disk options tab (which
> > you
> > > seem to have done already).
> > >
> > > Check this article on wiki as well...
> > > https://pve.proxmox.com/wiki/Shrink_Qcow2_Disk_Files
> > >
> > > Gianni
> > >
> > >
> > > On Tue, 9 Jul 2019 at 09:49, Mark Adams <mark at openvs.co.uk> wrote:
> > >
> > > > Hi All,
> > > >
> > > > Currently having an issue on a few servers where more space is being
> > > "used"
> > > > in the host (zfs), than is actually being used inside the VM. Discard
> > is
> > > > enabled, but zfs 0.7 does not have support for it.
> > > >
> > > > zfs 0.8 has brought in discard support, so I was wondering if anyone
> > else
> > > > has upgraded to it to resolve this kind of issue?
> > > >
> > > > I realise it's in proxmox 6, but I don't want to go there until it's
> > out
> > > of
> > > > beta.
> > > >
> > > > Any comments appreciated!
> > > >
> > > > Cheers,
> > > > Mark
> > > > _____________________________________________


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