topic Re: sar -d in Operating System - HP-UX

sar -d

Stephen Tatrai — Thu, 14 Sep 2000 18:27:29 GMT

I am running HP-UX 10.20. When running sar -d I noticed the following:

15:12:12 device %busy avque r+w/s blks/s avwait avserv
15:12:22 c4t6d0 3.60 0.50 3 33 5.05 31.34
c5t2d0 100.00 0.80 2 28 8.86 25.08
c1t0d0 0.30 0.50 0 3 6.02 15.49

Disk c5t2d0 is a mirror of c4t6d0
Why is it showing 100% utilization. I also have 3 other disk in the same situation. Glance does not show the disks as active.

Re: sar -d

Anthony deRito — Thu, 14 Sep 2000 18:39:57 GMT

The 100% BUSY means that the device is busy servicing I/O requests 100% of the interval time you specified. This in itself does not indicate a problem.

Tony

Re: sar -d

James R. Ferguson — Thu, 14 Sep 2000 18:42:57 GMT

Hi:

The 100% means that during the same period the disk was "always" busy servicing an I/O. More important is the queue depth (avque). If this is high, you have increasing performance degradation. I assume that the difference you see with Glance is related to different sample periods.

...JRF...

Re: sar -d

Stephen Tatrai — Thu, 14 Sep 2000 18:51:19 GMT

The rest of the sar parameters do not seem to imply any major activity to the disk.
I have run sar throughtout the day with an interval of 180 seconds and see the same results. Also the primary disk in the mirror shows little activity and I know the
disk should not have much activity.

Re: sar -d

TC ITEMS Unix Admin — Thu, 14 Sep 2000 18:52:57 GMT

Stephen:
As has been said, for the sampling period you chose, that was the disk activity... it is perfectly normal for disks in a mirror to have different disk activity rate. If you are really worried, you could run sar over diffent sampling rates.

you could also try iostat over various sampling periods.

Re: sar -d

John Palmer — Thu, 14 Sep 2000 20:06:59 GMT

There is no way that the disk could be 100% busy doing 2 transfers per second. sar is not always accurate - it is a 'standard' UNIX utility and in your case is not properly interpreting information retrieved from the kernel.

As you have got glance - believe it! It is specifically written to interface with the kernel (using different interfaces from sar).

If you also have measureware then there is no reason to use sar at all.

Re: sar -d

rajsri — Fri, 15 Sep 2000 00:05:38 GMT

hi
the best way is to monitor one days activity to cofirm what is real and fake .
use the following commnad in cron
0 * * * * /usr/lbin/sa/sa1 300 12
which will log all data in /var/adm/sa dir at the end of the day u can view the statistics.

Raj