Scalability problem with disk IO

[chetan a]

Hello,

I have a problem in scaling disk i/o. The machine is an 11i v2 itanium application server with two HP EVA's ( 75 gig, 15k rpm each).

AVerage values of sar output is given below,

c0t6d0 8.67 0.67 11 113 0.16 16.62
c127t0d7 78.73 0.52 716 24672 0.06 3.44
c80t0d3 77.73 0.51 700 24256 0.03 3.44
c57t1d2 77.03 0.51 722 24917 0.01 3.12
c32t0d6 78.71 0.51 737 25241 0.02 3.40
c95t0d2 77.69 0.51 721 24975 0.02 3.30
c102t1d1 79.77 0.51 973 39190 0.01 2.45
c53t0d5 78.73 0.51 726 24764 0.02 3.45
c16t0d1 77.59 0.51 718 24686 0.02 3.35
c102t1d3 70.10 0.50 3385 54153 0.00 0.21
c65t1d0 0.02 0.50 0 0 0.00 0.24

AVerage CPU usage using sar,

HP-UX rx8640f B.11.23 U ia64 03/05/07

13:02:38 %usr %sys %wio %idle
Average 30 13 32 25


I tried tweaking scsi_max_qdepth, but it was of no use. My cpu consumption is only around 40% but I am not able to scale up my I/O capcity.

How to determine the problem with IO, ?

Cheers,
Chetan