Re: iSeries Disk Pricing

Well, I thought the new drives had significantly better specs and could use the
SCSI-3 spec.

Even given that, it may be a surprise just how much faster a big drive is than a
smaller drive, purely due to data density. Not to be heretical or anything, but
the 400 world is somewhat overly fascinated with 'arms.'

The mainframe and AIX world are more concentrated on volumes - with the main
reason being that s/390 and AIX machines usually carry a lot more memory than
the iSeries machines, as well as much faster transfer rates on the controller.

I really truly expect this issue to even out quickly with the direction IBM is 
moving.

-Paul

----- Original Message -----
From: "Andy Nolen-Parkhouse" <aparkhouse@attbi.com>
To: <midrange-l@midrange.com>
Sent: Wednesday, May 01, 2002 8:48 AM
Subject: RE: iSeries Disk Pricing


> Paul,
>
> I agree with your point, but I'm not sure that the #4318 (17 GB 10K
> drive) and the #4317 (8.5 GB 10K) differ significantly in cache or data
> transfer characteristics.  The V5R1 Performance Capabilities Reference
> describes them as being similar but for capacity (it doesn't get
> specific on the characteristics you reference).  They are both Ultra2
> SCSI at 80 MB transfer rates.  I think that they are pretty much apples
> and apples in their performance characteristics.  So pending any
> announcements of new disk drives, I would stand by my main points.  I
> agree that room for expansion is a good thing, but in the case of many
> of the systems I configured, they already had room for many years of
> expansion using the 8 GB drives.
>
> Increasing system memory would provide significant throughput
> improvements for both 8 GB and 17 GB configurations.
>
> Syd,
>
> I agree with your point that other workloads, including those dealing
> with stream files, may not be affected as dramatically, my comments were
> referring specifically to DB2-based transaction serving, whether
> green-screen or client-server.
>
> Regards,
> Andy Nolen-Parkhouse
>
> > Subject: Re: iSeries Disk Pricing
> >
> > While the number of arms is of course, very important, the cache in
> the
> > DASD and the
> > speed with which the DASD can transfer data has a perhaps,
> unexpectedly
> > large impact
> > on overall performance.
> >
> > You *might* find that you only need 1/2 the number of arms to get the
> same
> > or better
> > performance. It depends a lot on your system and application, but that
> is
> > definitely a
> > possibility. As well as the fact that databases tend to grow and grow,
> and
> > DB/2, unlike
> > traditional file based systems, can also partition the data in better
> > ways, allowing you to
> > partition data for a particular system (or geographic location, or
> group
> > of users, etc.) over
> > a particular set of volumes.
> >
> > -Paul
>
> _______________________________________________
> This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list
> To post a message email: MIDRANGE-L@midrange.com
> To subscribe, unsubscribe, or change list options,
> visit: http://lists.midrange.com/cgi-bin/listinfo/midrange-l
> or email: MIDRANGE-L-request@midrange.com
> Before posting, please take a moment to review the archives
> at http://archive.midrange.com/midrange-l.
>
>