From: ronnie sahlberg <ronniesahlberg@gmail.com>
To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@gmail.com>
Subject: Re: [Qemu-devel] virtio-scsi vs. virtio-blk
Date: Fri, 10 Aug 2012 22:24:56 +1000 [thread overview]
Message-ID: <CAN05THT_uwYg5-fCEAqip7MerSbDXyGjj6PO73frxfOfrEPaBw@mail.gmail.com> (raw)
In-Reply-To: <5024FB17.7060706@profihost.ag>
On Fri, Aug 10, 2012 at 10:14 PM, Stefan Priebe - Profihost AG
<s.priebe@profihost.ag> wrote:
> 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.
I dont know the kvm version numbers.
But you can check the file
block/iscsi.c for the version you use for this :
.bdrv_aio_discard = iscsi_aio_discard,
If it has bdrv_aio_discard then you have support for 'discard' when
using the scsi emulation. i.e. -drive ...,if=scsi,...
#ifdef __linux__
.bdrv_ioctl = iscsi_ioctl,
.bdrv_aio_ioctl = iscsi_aio_ioctl,
#endif
If it has these two lines too, then you have scsi-passthrough and can
bypass the qemu scsi emulation.
One way to activate passthough is via scsi-generic:
Example:
-device lsi -device scsi-generic,drive=MyISCSI \
-drive file=iscsi://10.1.1.125/iqn.ronnie.test/1,if=none,id=MyI
regards
ronnie sahlberg
next prev parent reply other threads:[~2012-08-10 12:25 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-08 15:21 [Qemu-devel] virtio-scsi vs. virtio-blk Stefan Priebe
2012-08-08 16:17 ` Paolo Bonzini
2012-08-08 17:12 ` Stefan Priebe
2012-08-08 17:37 ` Paolo Bonzini
2012-08-09 6:13 ` Stefan Priebe
2012-08-09 7:01 ` Paolo Bonzini
2012-08-09 7:07 ` Stefan Priebe
2012-08-09 7:19 ` Paolo Bonzini
2012-08-09 7:41 ` Stefan Priebe
2012-08-09 7:53 ` Paolo Bonzini
2012-08-09 8:00 ` Stefan Priebe
2012-08-09 8:03 ` Paolo Bonzini
2012-08-09 9:18 ` Stefan Hajnoczi
2012-08-09 10:17 ` Stefan Priebe - Profihost AG
2012-08-09 11:04 ` Stefan Hajnoczi
2012-08-09 11:10 ` Paolo Bonzini
2012-08-09 11:24 ` Stefan Priebe - Profihost AG
2012-08-09 12:08 ` Stefan Priebe - Profihost AG
2012-08-09 12:19 ` Paolo Bonzini
2012-08-09 12:31 ` Stefan Priebe - Profihost AG
2012-08-09 12:44 ` Paolo Bonzini
2012-08-09 15:41 ` Stefan Priebe - Profihost AG
2012-08-09 12:52 ` ronnie sahlberg
2012-08-09 13:15 ` Paolo Bonzini
2012-08-09 13:39 ` Stefan Priebe - Profihost AG
2012-08-09 13:42 ` Paolo Bonzini
2012-08-09 13:52 ` Stefan Priebe - Profihost AG
2012-08-09 14:35 ` Paolo Bonzini
2012-08-09 14:25 ` Stefan Priebe - Profihost AG
2012-08-10 9:22 ` Stefan Priebe - Profihost AG
2012-08-10 10:20 ` Paolo Bonzini
2012-08-10 10:28 ` Stefan Priebe - Profihost AG
2012-08-10 10:30 ` Paolo Bonzini
2012-08-10 11:12 ` ronnie sahlberg
2012-08-10 11:57 ` Stefan Priebe - Profihost AG
2012-08-10 12:04 ` ronnie sahlberg
2012-08-10 12:14 ` Stefan Priebe - Profihost AG
2012-08-10 12:24 ` ronnie sahlberg [this message]
2012-08-10 12:35 ` Stefan Priebe - Profihost AG
2012-08-10 12:39 ` Paolo Bonzini
2012-08-10 12:43 ` Stefan Priebe - Profihost AG
2012-08-10 11:20 ` ronnie sahlberg
2012-08-10 11:54 ` Stefan Priebe - Profihost AG
2012-08-10 11:58 ` ronnie sahlberg
2012-08-10 12:38 ` Stefan Priebe - Profihost AG
2012-08-10 11:49 ` Stefan Priebe - Profihost AG
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