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Re: [Qemu-devel] virtio-scsi vs. virtio-blk
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] virtio-scsi vs. virtio-blk |
Date: |
Thu, 09 Aug 2012 15:15:41 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
Il 09/08/2012 14:52, ronnie sahlberg ha scritto:
>> >
>> > guest uses noop right now. Disk Host is nexentastor running open solaris. I
>> > use libiscsi right now so the disks are not visible in both cases
>> > (virtio-blk and virtio-scsi) to the host right now.
>> >
> And if you mount the disks locally on the host using open-iscsi, and
> access them as /dev/sg* from qemu, what performance do you get?
Good question.
> virtio-blk would first go to scsi emulation and then call out to
> block/iscsi.c to translate back to scsi commands to send to libiscsi
>
> while virtio-scsi (I think) would treat libiscsi as a generic scsi
> passthrough device. I.e. all commands just go straight through
> bdrv_aio_ioctl(SG_IO)
I think he's not using scsi-block or scsi-generic, because 1.0 libiscsi
didn't support that.
scsi-generic would indeed incur some overhead because it does not do
scatter/gather I/O directly, but scsi-hd/scsi-block do not have this
overhead. In any case, that should be visible through the output of
perf if it is significant.
Paolo
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, (continued)
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Hajnoczi, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, ronnie sahlberg, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk,
Paolo Bonzini <=
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/09
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/10
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/10
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Stefan Priebe - Profihost AG, 2012/08/10
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, Paolo Bonzini, 2012/08/10
- Re: [Qemu-devel] virtio-scsi vs. virtio-blk, ronnie sahlberg, 2012/08/10