Re: [ovirt-users] How do I get discard working?

Once upon a time, Fabian Deutsch <fdeutsch@redhat.com> said:

I'm not sure which qemu disk drivers/busses support this, but at least virtio does so. I'm using it for development.

Using CentOS 7, I think qemu-kvm only supports discard on virtio-scsi drives using the raw format. Discard on qcow2 images is supported for newer versions of qemu-kvm. oVirt uses virtio by default; you can switch to virtio-scsi. However, if you use thin-provisioned disks, oVirt uses qcow2 format, so discard is not supported with CentOS 7's version of qemu-kvm. -- Chris Adams <cma@cmadams.net>