From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bart Van Assche" Subject: Re: Integration of SCST in the mainstream Linux kernel Date: Thu, 31 Jan 2008 08:48:26 +0100 Message-ID: References: <20080130195635T.tomof@acm.org> <20080130225428S.tomof@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from rv-out-0910.google.com ([209.85.198.184]:18073 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755987AbYAaHs1 (ORCPT ); Thu, 31 Jan 2008 02:48:27 -0500 Received: by rv-out-0910.google.com with SMTP id k20so467584rvb.1 for ; Wed, 30 Jan 2008 23:48:26 -0800 (PST) In-Reply-To: <20080130225428S.tomof@acm.org> Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: fujita.tomonori@lab.ntt.co.jp, rdreier@cisco.com, James.Bottomley@hansenpartnership.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, vst@vlnb.net, linux-scsi@vger.kernel.org, scst-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org On Jan 30, 2008 2:54 PM, FUJITA Tomonori wrote: > On Wed, 30 Jan 2008 14:10:47 +0100 > "Bart Van Assche" wrote: > > > On Jan 30, 2008 11:56 AM, FUJITA Tomonori wrote: > > > > > > 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. > > I know that you use different hardware. I used 'ratio' word. Let's start with summarizing the relevant numbers from Robin's measurements and my own measurements. Maximum bandwidth of the underlying physical medium: 2000 MB/s for a DDR 4x InfiniBand network and 1000 MB/s for a SDR 4x InfiniBand network. Maximum bandwidth reported by the OFED ib_write_bw test program: 1473 MB/s for Robin's setup and 933 MB/s for my setup. These numbers match published ib_write_bw results (see e.g. figure 11 in http://www.usenix.org/events/usenix06/tech/full_papers/liu/liu_html/index.html or chapter 7 in http://www.voltaire.com/ftp/rocks/HCA-4X0_Linux_GridStack_4.3_Release_Notes_DOC-00171-A00.pdf) Throughput measured for communication via STGT + iSER to a remote RAM disk via direct I/O with dd: 800 MB/s for writing and 751 MB/s for reading in Robin's setup, and 647 MB/s for writing and 589 MB/s for reading in my setup. >>From this we can compute the I/O-performance to ib_write_bw bandwidth: 54 % for writing and 51 % for reading in Robin's setup, and 69 % for writing and 63 % for reading in my setup. Or a slightly better utilization of the bandwidth in my setup than in Robin's setup. This is no surprise -- the faster a communication link is, the harder it is to use all of the available bandwidth. So why did you state that in Robin's tests the I/O performance to line speed ratio was better than in my tests ? Bart Van Assche.