RE: CPW? vs System Performance -- MIDRANGE-L

Konrad,

CPW is a specific benchmark which measures iSeries performance on what
IBM considers a fairly standard business transaction workload.  While I
don't have specifics right at hand, it is a good measure of how a system
will perform running a green-screen ERP system with journaling active
(or similar 'traditional' iSeries workloads).  These workloads tend to
have quite a bit of database I/O and benefit from the balanced
multi-processor architecture of the AS/400.  IBM has some decent white
papers on CPW available on their web site.

There are quite a number of instances in server applications, notably
Domino and WebSphere, where an application reads something into memory
and then works on it intensively without doing much database I/O.  For
these applications, clock speed and cache size may have more impact on
performance than CPW.  CPW just wasn't designed to measure those
workloads.  I ran some Domino applications on a model 720 and found that
a 200 MHz Pentium did the job many times faster.  While this was not
true of general email applications in Domino, I had one custom
application which just wouldn't fly, it needed the clock speed.

The 270 models are more similar to the 8xx models than the 7xx.

Is there a particular decision you need to make?  Do you need to upgrade
an existing installed machine?

IBM doesn't really have 'server' models anymore.  Starting with the 7xx
generation of machines, they have configured various levels of
interactive performance into the machines as either base or optional
features.  CFINT still comes into play when the interactive level is
exceeded and will inhibit further interactive performance utilization.

Regards,
Andy Nolen-Parkhouse

> Subject: CPW? vs System Performance
>
> The discussion in the other thread about disk sizes, density, cache
and
> arms has been very interesting since we are facing the same issues.
> Now I have an email from IBM that really confuses me (as if the whole
> disk thing was not confusing enough)...
>
> o  1st Generation 8xx Processor was 2X the speed of the 7xx
Processors,
> 2nd Generation speed improved 20%, 3rd Generation more than 2X again.
>       When Under 80% CPU Utilization, a 1st Gen.  8xx processor with
the
> same CPW as a 7xx processor, will run twice as fast as the 7xx.
>             ie:  More Work with Better Response Times.
>       8xx Fast Clock Speed & L2 Cache is required for CPU Intensive
> Workloads, like Lotus Domino, WebSphere, Java, & e-Business.
>
> Is this correct? How does something with the same CPW run twice as
fast?
> What is the effect
> of CFINT in a server model? And is the 270 part of the solution or
problem
> (ie more 7xx than
> 8xx)?
>
> The PC server and Unix server area seems so much less complicated than
> this
> model.
> Big drives, fast processors, lots of cache = performance.
>
> So is CPW obsolete? I had always understood it was a measure of total
> system
> throughput,
> not just cpu capability.
>
> Regards
>
> Konrad Underkofler