On 01.11.2014 05:30, Dennis Jacobfeuerborn wrote: > > Hi, > I'm trying to find out how to enable fstrim support for libvirt/qemu > guests. Specifically I'm trying to enable this on a CentOS 7 host (qemu > 1.5). I searched the web but only found very vague information and no > clear documentation on the requirements or how to modify the guest xml > to enable discard/fstrim support. > > Can someone point me in the right direction? One thing that you'll need is the guest agent: http://wiki.libvirt.org/page/Qemu_guest_agent Then you can just use: # virsh domfstrim $dom Michal

On 11/3/2014 8:43 AM, Andrey Korolyov wrote: > On Mon, Nov 3, 2014 at 4:24 PM, Michal Privoznik <mprivozn(a)redhat.com&gt; > wrote: >> On 01.11.2014 05:30, Dennis Jacobfeuerborn wrote: >>> Hi, >>> I'm trying to find out how to enable fstrim support for libvirt/qemu >>> guests. Specifically I'm trying to enable this on a CentOS 7 host (qemu >>> 1.5). I searched the web but only found very vague information and no >>> clear documentation on the requirements or how to modify the guest xml >>> to enable discard/fstrim support. >>> >>> Can someone point me in the right direction? >> >> One thing that you'll need is the guest agent: >> >> http://wiki.libvirt.org/page/Qemu_guest_agent >> >> Then you can just use: >> >> # virsh domfstrim $dom >> >> Michal > ... and probably discard-aware block driver (although I cannot name > anything except virtio-blk which is not supporting trim or will not > support in the near future). Not sure to which part, guest-host > interaction or driver abilities, the initial question belongs. > > The virtio-scsi driver supports it, though you take a minor performance hit for switching.