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average disk Q metrix

dom kris
Frequent Advisor

average disk Q metrix

Helo,

does anybody have an idea how the average Q for a disk (avq) is calculated?
I need to compare the values from Collect to a third party product since the two products give completely different values.
I have looked at the 'hwmgr' cmd to get disk stats but I am unable to calculate the avq from this.
I looked on the Net to get some info but there is not much info about how disk Q are calculated.
If I have two different ways to get the avq for the disks, I can more easily the that third party product is wrong.
(if you know of another free tool apart from collect for Tru64 that gives you also the avq, it would also help)

any help much appreciated.

Kris
2 REPLIES
Dave Bechtold
Respected Contributor

Re: average disk Q metrix

Hi Kris,

I'm not exactly sure which collect disk stat you are referencing - I see no 'avq', nor am I familar with one. Here are the Disk Stats from collect man page.

Disks Section
___________________________________________________________
DSK An index into the table that collect outputs, used
for scripting.
NAME The name of the device, specified as dskinstance,
such as dsk23, and found in the system's /dev
directory.

B/T/L If this is a SCSI disk it contains the
Bus/Target/Lun identifier, otherwise a - (dash).
Use the hwmgr command to identify devices, as
described in the hwmgr(8) reference page.
R/S Reads per second.
RKB/S Kilobytes read per second.
W/S Writes per second.
WKB/S Kilobytes written per second.
AVS Average service time. The time spent actually ser-
vicing the request -no wait time in milliseconds.
AVW Average wait time. The time spent in the wait
queue in milliseconds.
ACTQ The number of requests in the active queue (that
is, being serviced by the disk).
WTQ The number of requests in the wait queue (have not
yet been submitted to disk).
%BSY Percent Busy. The time spent servicing requests in
interval divided by the interval.


The closest thing maybe the ACTQ - # Requests in the Active Queue for the disk.

Hope this helps.

Dave Bechtold
dom kris
Frequent Advisor

Re: average disk Q metrix

Hi Dave,

you are correct.
Collect does not have a avq stat, it is the sum of the ACTQ and the WTQ
Other Unix's use this 'avq' metric mostly with the 'sar' cmd.
But again, even for the actq and the wtq metrix in collect, I don't have any idea how they are calculated.

Kd