RE: New 270.

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Jenny,

The easiest way to check the activity on your disk arms is to use the
WRKDSKSTS display.  Pick a time which represents your peak load and
execute the command.  This will present an interactive status display.
Wait about half a minute, then refresh the statistics (F5).  One of the
columns will give the per cent busy.  Figure that forty per cent is the
maximum amount of activity which the system can tolerate before disk
arms become a limiting factor on overall performance.  If you're below
twenty on all of your drives then you're in good shape.

If you see a consistent disproportionate amount of activity on one or
two drives, then you might benefit from balancing your data using the
ASPBAL commands with the *USAGE parameters.  You should expect your
larger drives to have activity which is proportionate to their relative
size.  Given that an 8 GB drive will have twice the amount of stuff on
it as a 4 GB drive, it stands to reason that a given bit of data
required by a program is twice as likely to be on that drive and it
should see more activity.  This is not a problem; this is the way the
system is designed.  I don't know if the ASPBAL commands will compensate
for differing volume sizes.

Regards,
Andy Nolen-Parkhouse

> Subject: RE: New 270.
>
> How do you check the Disk Arm Utilisation?  Is this the way the system
> distributes data to the different disks?  If so is the impact on
> performance
> the time it takes to move between disks if the system is distributing
data
> in a given way between smaller and higher capacity disks?
>
> Sorry just a few basic questions from a beginner.  We have a variety
of
> different disk sizes and they all show equivalent % utilisation so how
do
> we
> know if the system is inefficient (apart from response time).
Response
> time
> is okay but how do you know if it could be better?