RE: DASD arm worksheets -- MIDRANGE-L

Thanks for the detail!

Any thoughts on the 40mb cache controllers vs. the 757mb cache controllers?

We're around a 200 user Domino shop and a Websphere App Server shop (with
very light usage).  The 2757 controller made a huge positive impact in
performance for Domino, but the previous card was a 5702 with NO cache at
all.


                                                                       
             "Kendall Kinnear"                                         
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IBM has changed to a I/O per second calculation for sizing disk on the
newer models. The way I do it is to collect performance data to determine
the current average I/Os per second. I then add a growth factor and
multiply that by the number of drives on the system. I then divide that
number by the number of I/Os per second the new disk subsystem can support
per drive. That can be anywhere from 40 to 60 depending on how conservative
you want to be. This will give an estimate of the number of drives to
propose.

Kendall Kinnear
Consulting System i5 Architect
Stonebridge

Phone: 214-676-3146
email:   kendall.kinnear@xxxxxxxx

Sent from Windows Mobile 5

-----Original Message-----
From: "ChadB@xxxxxxxxxxxxxxxxxxxx" <ChadB@xxxxxxxxxxxxxxxxxxxx>
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Sent: 5/2/06 10:13 AM
Subject: DASD arm worksheets


Does anyone know if IBM still publishes the "DASD Arms Required for
Performance" type worksheets for the i5 models?  I've used them in the past
as an additional measure of insurance when designing a new system, but the
last time I used one was for an 800.  We're starting to spec out a new 520
to replace the 800 and with the Domino and Websphere workloads I KNOW we've
had disk arm/controller issues in the past, so I want to ensure a good
config.  The 800 was originally spec'ed by the previous admin/BP with a
5702 controlling 6 mirrored drives and the box performed horribly.  I got
it switched over to a RAIDed 2757 and made a positive impact (and want that
to carry over to the new box!).

In addition to the DASD arms worksheet, i'm looking for some input on the
757mb cache and 40mb cache RAID controllers available for the i5s.  We're
hoping to keep this box to just a system enclosure and I think with the
520s all the 757mb controllers are not permitted in the system enclosure.
Is this true?  If so, i'm wondering how a 40mb controller will fare in
comparison to the current 2757 (757mb cache) we're running.  I would hate
to take a step backwards on the disk cache... Domino seems to love the
increased disk cache.
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