Disk I/O Utlisation

[Stuart Abramson_2]

11:18:20device..%busy...avque...r+w/s...blks/s..avwait..avserv
11:28:20c2t5d0..7.59....0.50....7.......63......4.35....15.27
........c1t11d0.0.79....0.50....1.......5.......4.95....10.91
........c2t3d0..0.01....0.50....0.......0.......4.52....13.00
........c7t14d0.4.53....0.50....5.......54......4.49....10.66
........c0t0d0..0.22....0.50....0.......6.......5.35....12.68
........c0t1d0..1.84....0.50....2.......7.......5.00....10.16
........c0t3d0..0.09....0.50....0.......2.......0.92....12.57
........c0t4d0..0.83....0.50....1.......3.......4.92....11.93
........c0t5d0..1.81....0.50....2.......15......4.94....7.83
........c1t0d0..0.09....0.50....0.......2.......0.96....13.32
........c1t1d0..0.13....0.50....0.......3.......3.32....11.67
........c1t5d0..0.58....0.50....1.......2.......4.86....12.95
........c1t4d0..0.92....0.50....1.......3.......5.21....16.67
........c1t3d0..0.22....0.50....0.......7.......4.44....13.48
........c1t2d0..0.36....0.50....0.......2.......5.10....11.20
........c0t2d0..2.53....0.50....2.......10......5.11....13.28
........c0t12d0.0.18....0.50....0.......2.......2.92....15.23
........c0t13d0.25.49...0.51....37......589.....5.03....7.30
........c1t13d0.1.95....0.60....2.......36......5.21....14.30
........c2t4d0..0.19....0.50....0.......2.......2.89....13.18
........c0t14d0.0.49....0.50....1.......6.......4.10....14.34
........c0t15d0.0.14....0.50....0.......2.......4.49....18.65

For this timestamp that you list:

1. % busy: None of your disks is busier than 25%. So that's not busy.
2. avque is 0.50 for all disks. So that means that the disks are not
backing up.
3. R+W/s is low. So, again, you're not busy.
4. blks/s, likewise, is low. (This is NOT sufficient load to measure
your disks!)
5. avwait is low, given rotation speeds in the 10,000 rpm range.
6. Your avser is higher than 6 ms. I forget what kind of disks you have,
but this probably means that you just have slow disks (compared to
10,000 rpm). One time that avserv does drop below 10 ms, is when you do
have some activity on c0t13d0. You probably got some sequential
streaming going.

In short, this timestamp isn't strenuous enough to tell you much.

[John Jayaseelan]

Stuart,

Following is the average taken for more than 1 hour. The point 'sequential activity' is what my opnion also. This disks are connected through 2 SCSI FW controller. It looks like the bottleneck is the traffic through the controller not actual disks.

dd on a 2GB disk took 270 seconds which is supposed to be 100 seconds on 20MB/Sec FW SCSI controller. Is there soln?

# sar -d 600 10

HP-UX ccprod01 B.11.00 U 9000/898 12/05/03

device %busy avque r+w/s blks/s avwait avserv
Average c2t5d0 8.49 0.55 8 72 4.83 15.82
Average c1t11d0 0.65 0.50 1 4 5.00 10.87
Average c2t3d0 0.02 0.50 0 0 5.53 13.07
Average c7t14d0 5.22 0.55 6 61 4.89 11.44
Average c0t0d0 0.23 0.50 0 5 4.91 10.47
Average c0t1d0 0.99 0.50 2 18 5.06 4.79
Average c0t3d0 0.10 0.50 0 2 1.77 12.52
Average c0t4d0 0.62 0.50 1 9 5.03 8.51
Average c0t5d0 1.81 0.50 6 59 5.08 3.11
Average c1t0d0 0.08 0.50 0 1 1.50 12.76
Average c1t1d0 0.13 0.50 0 3 3.32 13.29
Average c1t5d0 0.36 0.50 0 2 4.95 13.30
Average c1t4d0 0.45 0.50 0 2 4.95 15.05
Average c1t3d0 0.21 0.50 0 6 4.02 13.40
Average c1t2d0 0.19 0.50 0 1 5.08 10.22
Average c0t2d0 1.81 0.50 3 22 5.03 7.87
Average c0t12d0 0.22 0.50 0 2 4.10 13.35
Average c0t13d0 8.81 0.63 12 179 5.65 9.49
Average c1t13d0 1.75 1.20 2 30 8.69 17.32
Average c2t4d0 0.25 0.50 0 3 3.83 11.38
Average c0t14d0 0.79 0.82 1 8 7.15 19.78
Average c0t15d0 0.19 0.50 0 2 4.51 19.31
Average c1t14d0 0.51 0.87 1 6 6.78 17.43
Average c1t15d0 0.13 0.50 0 2 4.41 16.75

Thanks