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Re: [Qemu-devel] IO performance test on the tcm-vhost scsi
From: |
Cong Meng |
Subject: |
Re: [Qemu-devel] IO performance test on the tcm-vhost scsi |
Date: |
Thu, 14 Jun 2012 17:57:34 +0800 |
On Wed, 2012-06-13 at 12:08 -0700, Nicholas A. Bellinger wrote:
> On Wed, 2012-06-13 at 18:13 +0800, mengcong wrote:
> > Hi folks, I did an IO performance test on the tcm-vhost scsi. I want to
> > share
> > the test result data here.
> >
> >
> > seq-read seq-write rand-read rand-write
> > 8k 256k 8k 256k 8k 256k 8k 256k
> > ----------------------------------------------------------------------------
> > bare-metal 67951 69802 67064 67075 1758 29284 1969 26360
> > tcm-vhost-iblock 61501 66575 51775 67872 1011 22533 1851 28216
> > tcm-vhost-pscsi 66479 68191 50873 67547 1008 22523 1818 28304
> > virtio-blk 26284 66737 23373 65735 1724 28962 1805 27774
> > scsi-disk 36013 60289 46222 62527 1663 12992 1804 27670
> >
> > unit: KB/s
> > seq-read/write = sequential read/write
> > rand-read/write = random read/write
> > 8k,256k are blocksize of the IO
> >
> > In tcm-vhost-iblock test, the emulate_write_cache attr was enabled.
> > In virtio-blk test, cache=none,aio=native were set.
> > In scsi-disk test, cache=none,aio=native were set, and LSI HBA was used.
> >
> > I also tried to do the test with a scsi-generic LUN (pass through the
> > physical partition /dev/sgX device). But I couldn't setup it
> > successfully. It's a pity.
> >
> > Benchmark tool: fio, with ioengine=aio,direct=1,iodepth=8 set for all tests.
> > kvm vm: 2 cpus and 2G ram
> >
>
> These initial performance results look quite promising for virtio-scsi.
>
> I'd be really interested to see how a raw flash block device backend
> that locally can do ~100K 4k mixed R/W random IOPs compares with
> virtio-scsi guest performance as the random small block fio workload
> increases..
flash block == Solid state disk? I have no one on hand.
>
> Also note there is a bottleneck wrt to random small block I/O
> performance (per LUN) on the Linux/SCSI initiator side that is effecting
> things here. We've run into this limitation numerous times with using
> SCSI LLDs as backend TCM devices, and I usually recommend using iblock
> export with raw block flash backends for achieving the best small block
> random I/O performance results. A number of high performance flash
> storage folks do something similar with raw block access (Jen's CC'ed)
>
> As per Stefan's earlier question, how does virtio-scsi to QEMU SCSI
> userspace compare with these results..? Is there a reason why these
> where not included in the initial results..?
>
This should be a mistake I made. I will do this pattern later.
> Thanks Meng!
>
> --nab
>