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Date: Thu, 09 Aug 2012 14:19:04 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] virtio-scsi vs. virtio-blk
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To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel <qemu-devel@nongnu.org>

Il 09/08/2012 14:08, Stefan Priebe - Profihost AG ha scritto:
> 
> virtio-scsi:
> rand 4k:
>   write: io=822448KB, bw=82228KB/s, iops=20557, runt= 10002msec
>   read : io=950920KB, bw=94694KB/s, iops=23673, runt= 10042msec
> seq:
>   write: io=2436MB, bw=231312KB/s, iops=56, runt= 10784msec
>   read : io=3248MB, bw=313799KB/s, iops=76, runt= 10599msec
> 
> virtio-blk:
> rand 4k:
>   write: io=896472KB, bw=89051KB/s, iops=22262, runt= 10067msec
>   read : io=1710MB, bw=175073KB/s, iops=43768, runt= 10002msec
> seq:
>   write: io=4008MB, bw=391285KB/s, iops=95, runt= 10489msec
>   read : io=5748MB, bw=570178KB/s, iops=139, runt= 10323msec

Thanks; some overhead is expected, but not this much.  Especially the
sequential case is bad, what disk is this?

Things to test include:

- using the deadline I/O scheduler on at least the host, and possibly
the guest too

- running perf on the guest and the host (separately) to get profiles

Paolo