RE: Subject: DASD Replacement

Yes, there can be severe performance issues regarding replacing 60 drives
with 25 drives.  Many systems require a certain number of disk arms in
order to perform adequately.  There is no way of knowing from your
description whether your system would have a problem or not.  Certainly
you will be doing the same amount of disk accesses with less than half
the number of disk arms.

The disk arm calculator which Marco mentioned is a good place to start.
If you have Performance Tools installed, run a sample during your busiest
period and find out what your average disk arm utilization is.  Or you
could spend some time on the WRKDSKSTS display and try to see what your
utilization is.  If you are between fifteen and twenty per cent and you
cut the number of disk arms by more than half, then there is a good
chance that you will severely affect performance by your plan.

It's probably important enough that if you don't get a clear result that
you should hire a consultant to look at it or get some expert advice in
some other way.  You are spending a lot of money to replace your drives
and it could have a large negative effect.

Kind Regards and Good Luck,
Andy Nolen-Parkhouse

> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-
> bounces@xxxxxxxxxxxx] On Behalf Of MIDRANGE
> Sent: Monday, March 10, 2003 9:05 PM
> To: MIDRANGE-L@xxxxxxxxxxxx
> Subject: Subject: DASD Replacement
> 
> We are planning to replace 60 unit 4317 DASD ( 8.58 GB) with 25 unit
> 4319 DASD ( 35.16 GB) in our 830 (OS V5R1). Is there any performance
> issue regarding this replacement?
> 
> Heriyanto Hudoyo (herih@xxxxxxxxxxxx)
> Niaga - Indonesia