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

[Matthias Leopold]

Am 2018-01-20 um 19:54 schrieb Yaniv Kaul:



On Jan 19, 2018 3:29 PM, "Matthias Leopold" 
> 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
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Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property

[Yaniv Kaul]

On Mon, Jan 22, 2018 at 6:53 AM, Zip <pl...@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-boun...@ovirt.org> on behalf of Yaniv Kaul <yk...@redhat.com>
> Date: Saturday, January 20, 2018 at 12:54 PM
> To: Matthias Leopold <matthias.leop...@meduniwien.ac.at>
> Cc: Wolfgang Lendl <wolfgang.le...@meduniwien.ac.at>, Ovirt Users <
> users@ovirt.org>
> Subject: Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property
>
>
>
> On Jan 19, 2018 3:29 PM, "Matthias Leopold" <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.
>
>
> oVirt version: 4.1.8
>
> Thanks
> Matthias
>
> ___
> Users mailing list
> Users@ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
>
>
>
>
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Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property

[Zip]

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

Zip



From:  <users-boun...@ovirt.org> on behalf of Yaniv Kaul <yk...@redhat.com>
Date:  Saturday, January 20, 2018 at 12:54 PM
To:  Matthias Leopold <matthias.leop...@meduniwien.ac.at>
Cc:  Wolfgang Lendl <wolfgang.le...@meduniwien.ac.at>, Ovirt Users
<users@ovirt.org>
Subject:  Re: [ovirt-users] VirtIO-SCSI and viodiskcache custom property



On Jan 19, 2018 3:29 PM, "Matthias Leopold"
<matthias.leop...@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
> 
> ___
> Users mailing list
> Users@ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
> 
> 



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

[Yaniv Kaul]

On Jan 19, 2018 3:29 PM, "Matthias Leopold" <
matthias.leop...@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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[ovirt-users] VirtIO-SCSI and viodiskcache custom property

[Matthias Leopold]

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.

oVirt version: 4.1.8

Thanks
Matthias

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