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

[Stefan Priebe - Profihost AG]

Am 09.08.2012 14:19, schrieb Paolo Bonzini:
> 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?

right now this is an external iscsi Nexentastor. Locally i can't get 
this bandwith nor these iops to test.


> Things to test include:
>
> - using the deadline I/O scheduler on at least the host, and possibly
> the guest too
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.

> - running perf on the guest and the host (separately) to get profiles
Which command of perf? Just perf top?

Stefan