RE: Disk arms and faulting: (was - We've Added more memory...but I can't remember!)

Reducing activity levels will reduce memory requirements, thus reducing
faulting.  This is something most administrators miss.  Lower your activity
levels until you start seeing Active to Ineligible faults.  Increase back to
where that does not happen.  A low Wait to Ineligible can be acceptable.  If
not, increase memory and/or activity levels.  It really becomes a balancing
act when you do not have the resources for the work load.  If unacceptable
faulting happens for a short time during peak usage, you might be able to
spread your work load out over a longer period.  More disk arms help high
fault rates hurt less.  If your drive are overworked, active jobs will move
to a long wait state waiting on data to process from disk, thus get paged
out of memory, thus causing higher disk are usages.  A catch 22.

Christopher K. Bipes      mailto:Chris.Bipes@Cross-Check.com
Operations & Network Mgr  mailto:Chris_Bipes@Yahoo.com
CrossCheck, Inc.          http://www.cross-check.com
6119 State Farm Drive     Phone: 707 586-0551 x 1102
Rohnert Park CA  94928    Fax: 707 586-1884


-----Original Message-----
From: Andy Nolen-Parkhouse [mailto:aparkhouse@attbi.com]
Sent: Friday, July 12, 2002 2:22 AM

I do not understand the impact of too few disk arms on faulting.

So while I can see the effect that faulting would have on disk activity,
I don't see the effect of disk activity on faulting.  Other than
tinkering with expert cache, adjusting your workload, or changing your
activity levels, what can you do about faulting/paging other than
increase memory?