[ovirt-users] VirtIO-SCSI and viodiskcache custom property

[Yaniv Kaul]

On Mon, Jan 22, 2018 at 6:53 AM, Zip <plord at intricatenetworks.com> wrote:

> Does it help if you edit the VM and under Resource Allocation – enable IO
> threads. ?
>

Confusingly, it has nothing to do with IO threads.
Y.


>
> Zip
>
>
>
> From: <users-bounces at ovirt.org> on behalf of Yaniv Kaul <ykaul at redhat.com>
> Date: Saturday, January 20, 2018 at 12:54 PM
> To: Matthias Leopold <matthias.leopold at meduniwien.ac.at>
> Cc: Wolfgang Lendl <wolfgang.lendl at meduniwien.ac.at>, Ovirt Users <
> users at ovirt.org>
> Subject: Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property
>
>
>
> On Jan 19, 2018 3:29 PM, "Matthias Leopold" <matthias.leopold at meduniwien.
> ac.at> wrote:
>
> Hi,
>
> is there a reason why the viodiskcache custom property isn't honored when
> using VirtIO-SCSI?
>
> On a Cinder (Ceph) disk "viodiskcache=writeback" is ignored with
> VirtIO-SCSI and honored when using VirtIO.
>
> On an iSCSI disk "viodiskcache=writeback" is ignored with VirtIO-SCSI and
> the VM can't be started when using VirtIO with "unsupported configuration:
> native I/O needs either no disk cache or directsync cache mode, QEMU will
> fallback to aio=threads"
>
> We actually want to use "viodiskcache=writeback" with Cinder (Ceph) disks.
>
>
> That's because on block storage we use native io and not threads. I assume
> the hook needs to change to use native io in this case.
> Y.
>
>
> oVirt version: 4.1.8
>
> Thanks
> Matthias
>
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