Setting larger maxphys has in my experience made quite a difference, depending on the target. (actually on x64 it makes it slower). Generally, performance increases as the transfer size increases has been my observation, for some classes of targets. This is likely due to the target's ability to seek and process a single large request (for example, some targets won't cluster 8x1MB requests into a single operation).
Henry Newman of Instrumental reported some time back that he has observed gains all the way up to 32MB for sequntial I/O on high end HPC oriented arrays. Regards, Richard. On Sat, Apr 29, 2006 at 06:12:07AM -0700, Robert Milkowski wrote: > "But even > if you set it to 8 Mbytes, the protocol overhead per transfer is > so small that the performance gains will be barely noticeable." > > Well, i can't agree. v440 with 3510 JBOD with 15K 73GB disks, connected with > two links (MPxIO). > > bash-3.00# dd if=/dev/zero of=/dev/rdsk/c5t500000E0119495A0d0s0 bs=1024k > extended device statistics > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 63.8 0.0 65381.4 0.0 1.0 0.0 15.0 0 96 ssd193 > extended device statistics > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 66.2 0.0 67753.5 0.0 1.0 0.0 14.5 0 96 ssd193 > extended device statistics > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 63.0 0.0 64521.3 0.0 1.0 0.0 15.2 0 96 ssd193 > > > bash-3.00# dd if=/dev/zero of=/dev/rdsk/c5t500000E0119495A0d0s0 bs=8192k > > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 9.8 0.0 80642.8 0.0 0.9 0.0 93.7 0 92 c5 > 0.0 9.8 0.0 80641.9 0.0 0.9 0.0 93.7 0 92 > c5t500000E0119495A0d0 > extended device statistics > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 10.2 0.0 83267.8 0.0 0.9 0.0 91.1 0 93 c5 > 0.0 10.2 0.0 83268.1 0.0 0.9 0.0 91.1 0 93 > c5t500000E0119495A0d0 > extended device statistics > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device > 0.0 9.8 0.0 80552.4 0.0 0.9 0.0 93.8 0 92 c5 > 0.0 9.8 0.0 80551.6 0.0 0.9 0.0 93.8 0 92 > c5t500000E0119495A0d0 > > So 1024KB is about 25% slower in this case. > > > This message posted from opensolaris.org > _______________________________________________ > perf-discuss mailing list > perf-discuss@opensolaris.org -- :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-: Richard Mc Dougall : [EMAIL PROTECTED] Performance and Availability : x31542 Engineering : http://devnull.eng Sun Microsystems Inc : +1 650 352 6438 :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-: _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
