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Date: Thu, 09 Aug 2012 17:41:31 +0200
From: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
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Subject: Re: [Qemu-devel] virtio-scsi vs. virtio-blk
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel <qemu-devel@nongnu.org>

OK VMs do work fine now. Sorry for missing the patch after switching to 
qemu-kvm.

Am 09.08.2012 14:44, schrieb Paolo Bonzini:
> Ok, try deadline in the guest then.  Using noop amplifies bad
> performance, because you lose request merging.  With no host scheduler,
> as is the case with libiscsi, noop is rarely a good idea.

Tests with cache=none and deadline:
virtio-scsi:
   write: io=8267MB, bw=94023KB/s, iops=23505, runt= 90032msec
   read : io=14576MB, bw=165783KB/s, iops=41445, runt= 90035msec
   write: io=21312MB, bw=240782KB/s, iops=58, runt= 90636msec
   read : io=48072MB, bw=544882KB/s, iops=133, runt= 90342msec

virtio-blk:
   write: io=9210MB, bw=104710KB/s, iops=26177, runt= 90070msec
   read : io=18804MB, bw=213929KB/s, iops=53482, runt= 90006msec
   write: io=29080MB, bw=329478KB/s, iops=80, runt= 90379msec
   read : io=26328MB, bw=298159KB/s, iops=72, runt= 90421msec

So this looks OK to me. Do you agree? So with virtio-scsi discard should 
work?

Greets and many thanks
Stefan