Bart Van Assche wrote: > On Mon, Mar 10, 2008 at 3:20 PM, Doron Shoham <[EMAIL PROTECTED]> wrote: >> I used the following commands: >> for write commands: >> sgp_dd of=/dev/sg1 if=/dev/zero bs=512 bpt=<from 2-512> thr=8 time=1 >> count=20M >> for read commands >> sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=<from 2-512> thr=8 time=1 >> count=20M >> >> And the results are (all in MB/s): >> bpt: 2 4 8 16 32 64 128 256 >> 512 >> Write 22.5 41.4 80.6 160 275 443 570 740 >> 810 >> Read 42 80 170 313 550 940 1200 >> 1312 1300 >> >> What can be the reason for such difference between the bandwidth of Read >> and Write commands? > > Can you please try to use direct I/O instead of buffered I/O ? > > Bart.
I have tried to use dio but when the bpt was 128 (or higher) I got the following error: echo 1 > /proc/scsi/sg/allow_dio sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=128 thr=8 time=1 count=5M dio=1 time to transfer data was 2.236290 secs, 1200.36 MB/sec 5242880+0 records in 5242880+0 records out >> Direct IO requested but incomplete 40960 times Doron _______________________________________________ ewg mailing list ewg@lists.openfabrics.org http://lists.openfabrics.org/cgi-bin/mailman/listinfo/ewg