[PVE-User] zfs 0.7 no discard

Mark Adams mark at openvs.co.uk
Tue Jul 9 22:00:00 CEST 2019


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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> >
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