On Jan 30, 2008 2:54 PM, FUJITA Tomonori <tomof@xxxxxxx> wrote: > On Wed, 30 Jan 2008 14:10:47 +0100 > "Bart Van Assche" <bart.vanassche@xxxxxxxxx> wrote: > > > On Jan 30, 2008 11:56 AM, FUJITA Tomonori <tomof@xxxxxxx> 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. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
