Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property
Am 2018-01-20 um 19:54 schrieb Yaniv Kaul:
On Jan 19, 2018 3:29 PM, "Matthias Leopold"
<matthias.leopold(a)meduniwien.ac.at
<mailto:matthias.leopold@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.
Thank you, but i still don't quite get what's missing.
We want to use the combination of Cinder (Ceph) + cache=writeback +
VirtIO-SCSI. Would this be possible if aio=native was used (which is not
configurable)? With iSCSI storage you still get cache=none when using
VirtIO-SCSI and "viodiskcache=writeback" (and aio=native). Should i file
a bug report for the Cinder disk situation?
Thanks again
Matthias