"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.
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