Re: Integration of SCST in the mainstream Linux kernel

Bart Van Assche
2008-01-30T13:11:04Z

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 ratio 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.

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.

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

Bart.