Hi Ted,
I won't discount that could be true with an unusual pathologically SMP
unfriendly workload but it's not normal on modern zSeries environments
in my experience. The support in z/OS for more than 16 CP's would be
pointless if it were true. Some of the capacity charts produced for
z990 and z9 were questionable straight line plots but many workloads can
effectively use more than 16 general purpose CP's in a single z/OS
image. This is certainly true with a couple of the production LPARs I
have right at hand which are running 16 engines with IRD now and will
soon be scaled up further soon. I regularly review capture ratio and run
Cheryl's Boxscore reports across big upgrade or change events and I know
for a fact I am not throwing 1/3 of this box away. Two LPAR's with 18
CP's shared 16 @ using IRD on a z9 LPAR overhead is very low, capture
ratio is very low, this machine spends most of it's cycles running
business workloads. The SMP effect is simply not observed anywhere near
the scale you suggest. The idea you cannot efficiently use more than 8
or 12 engines is FUD that dates back to decades old quotes attributed to
Gene Amdahl. Modern CICS, IMS, DB2 workloads run very well in a wide
SMP environment.
Best Regards,
Sam Knutson, GEICO
Performance and Availability Management
mailto:[EMAIL PROTECTED]
(office) 301.986.3574
Basic Flying Rules:
1. Try to stay in the middle of the air.
2. Do not go near the edges of it.
3. The edges of the air can be recognized by the appearance of ground,
buildings, sea, trees and interstellar space. It is much more difficult
to fly there.
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On
Behalf Of Ted MacNEIL
Sent: Friday, June 09, 2006 8:00 PM
To: [email protected]
Subject: Re: One or two CPUs - the pros & cons
>First, for the past 10 years or so the SMP effect has been negated to
the point that it is "almost" not worth figuring, especially for
anything under 10 engines.
I disagree.
I lose 12-15% of the engine when I add the second one and I lose another
15% (or more) for each engine thereafter, up to about 8 or 9 engines.
Going from a 308 to a 309 adds only about 300 MIPS when an engine is
(nominally) 450 MIPS.
That to me is more than "almost" not worth figuring.
Unless you like losing 1/3 of an engine?
-
-teD
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