What does the following %wio numbers mean ? In other words, in this
case on avg 50% of cpu time is waitiing to IO (which means CPU is idle
during the time). But how does this number derived ? Avg of what or how
to narrow down to specfic disk or disks. I have 100s of EMC disks each
perform reasonably well (less than 5ms for avg service time and avg
wait time) but still the system is very slow. sar -d shows that all
disks are doing very good.

00:00:00 %usr %sys %wio %idle
.................
.................
14:00:00 27 4 51 17
14:10:00 34 6 47 13
14:20:00 47 7 40 6
14:30:00 38 6 48 8
14:40:00 32 6 52 10
14:50:00 26 6 56 13
15:00:00 24 5 56 14
15:10:00 27 8 52 14
15:20:00 28 6 55 12
15:30:00 34 7 48 11
15:40:00 30 7 52 11
15:50:00 29 7 54 11
16:00:00 34 6 47 13
16:10:00 35 6 44 15
16:20:00 34 6 47 13
16:30:00 36 6 45 13

Thanks!