Re: [Qemu-devel] virtio-scsi vs. virtio-blk

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Am 10.08.2012 14:04, schrieb ronnie sahlberg:
> On Fri, Aug 10, 2012 at 9:57 PM, Stefan Priebe - Profihost AG
> <s.priebe@profihost.ag> wrote:
>> Am 10.08.2012 13:12, schrieb ronnie sahlberg:
>>
>>> You want discard to work?
>>
>> Yes
>>
>>
>>> You are using qemu 1.0 ?
>>
>> actual qemu-kvm git
>>
>>
>>> So you dont have the qemu support for scsi-generic passthrough to iscsi
>>> devices.
>>
>> Why?
>>
>
> scsi-generic passthrough I think was added for iscsi in 1.1
> so in 1.0 your guest will talk scsi to qemu, and invoke the
> scsi-emulation in qemu.
> It then will call functions like 'bdrv_aio_discard()" in libiscsi
> that will translate it back into a scsi command again and pass it to
> the target.
>
> It still works, it just means you have a small degradation of
> performance compared to if you could send the SCSI CDB straight
> through to the iscsi target as you can in qemu 1.1
> Very likely so small performance hit that you can not even measure it.

which version are you talking about? I use qemu-kvm.git so this is 
upcomming 1.2 and i use libiscsi 1.5.0.

Greets,
Stefan