Re: Integration of SCST in the mainstream Linux kernel

[FUJITA Tomonori <tomof@acm.org>]

On Wed, 30 Jan 2008 14:10:47 +0100
"Bart Van Assche" <bart.vanassche@gmail.com> wrote:

> On Jan 30, 2008 11:56 AM, FUJITA Tomonori <tomof@acm.org> wrote:
> > On Wed, 30 Jan 2008 09:38:04 +0100
> > "Bart Van Assche" <bart.vanassche@gmail.com> wrote:
> > >
> > > Please specify which parameters you are referring to. As you know I
> >
> > Sorry, I can't say. I don't know much about iSER. But seems that Pete
> > and Robin can get the better I/O performance - line speed ratiwo with
> > STGT.
> 
> Robin Humble was using a DDR InfiniBand network, while my tests were
> performed with an SDR InfiniBand network. Robin's results can't be
> directly compared to my results.

I know that you use different hardware. I used 'ratio' word.


BTW, you said the performance difference of dio READ is 38% but I
think it's 27.3 %, though it's still large.


> Pete Wyckoff's results
> (http://www.osc.edu/~pw/papers/wyckoff-iser-snapi07-talk.pdf) are hard
> to interpret. I have asked Pete which of the numbers in his test can
> be compared with what I measured, but Pete did not reply.
> 
> > The version of OpenIB might matters too. For example, Pete said that
> > STGT reads loses about 100 MB/s for some transfer sizes for some
> > transfer sizes due to the OpenIB version difference or other unclear
> > reasons.
> >
> > http://article.gmane.org/gmane.linux.iscsi.tgt.devel/135
> 
> Pete wrote about a degradation from 600 MB/s to 500 MB/s for reads
> with STGT+iSER. In my tests I measured 589 MB/s for reads (direct
> I/O), which matches with the better result obtained by Pete.

I don't know he used the same benchmark software so I don't think that
we can compare them.

All I tried to say is the OFED version might has big effect on the
performance. So you might need to find the best one.


> Note: the InfiniBand kernel modules I used were those from the
> 2.6.22.9 kernel, not from the OFED distribution.

I'm talking about a target machine (I think that Pete was also talking
about OFED on his target machine). STGT uses OFED libraries, I think.