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  2. MIDRANGE-L
  3. May 2006

RE: DASD arm worksheets

Here's my method, I use the component report or DSPPFRDTA command out of
performance tools to determine the time interval to be used for the
measurement. I'm looking for an interval with high I/O rates and heavy
system utilization. The intervals to look at are primarily a judgment
call based on experience and an understanding of the workload on the
system. From there I run the disk I/O section of the System Report for
that specific interval to obtain the average I/Os per second. I repeat
this process over several intervals on different days to validate the
data. I am sure that Performance Navigator and other performance tools
offer this capability as well, I just haven't used them.

I hope that helps. 

Kendall Kinnear
System i5 Architect
Stonebridge
 
Direct Telephone Number: 972.419.7709
Or Toll Free:  800.776.9755 x7709
Cell Phone Number:  214-676-3146
Fax Number:  972.455.7260
Kendall.Kinnear@xxxxxxxx
http://www.SBTI.com/
If you are interested in iSeries and application development, follow
Angus' blog at http://www.angustheitchap.com/
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
ChadB@xxxxxxxxxxxxxxxxxxxx
Sent: Tuesday, May 02, 2006 11:46 AM
To: Midrange Systems Technical Discussion
Subject: RE: DASD arm worksheets


Yeah, the problem is that what's required starts to snowball.  Extra PCI
slot, expansion unit, more maintenance cost for the expansion unit, etc.
This is a simple box and we hate to have to go into an expansion
cabinet.
I'm just wondering what the hit will be like to go from the 757mb to the
40mb cache.

How do I find the current average I/O per second stat that Kendall is
referencing?  Does this need to be averaged over a period of time to be
useful for sizing?


 

             "Haase, Justin

             C."

             <justin.haase@Kin
To 
             gland.com>                "Midrange Systems Technical

             Sent by:                  Discussion"

             midrange-l-bounce         <midrange-l@xxxxxxxxxxxx>

             s@xxxxxxxxxxxx
cc 
 

 
Subject 
             05/02/2006 12:00          RE: DASD arm worksheets

             PM

 

 

             Please respond to

             Midrange Systems

                 Technical

                Discussion

             <midrange-l@midra

                 nge.com>

 

 





2780 with cache backup is the only way to go - WOW - it's amazing.  If
you've got the funds available, GET THEM!

--
Justin C. Haase - iSeries System Engineer
IBM Certified Systems Expert - System i
Kingland Systems Corporation

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of
ChadB@xxxxxxxxxxxxxxxxxxxx
Sent: Tuesday, May 02, 2006 10:50 AM
To: Midrange Systems Technical Discussion
Subject: RE: DASD arm worksheets


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"

             <Kendall.Kinnear@

             SBTI.com>
To
             Sent by:                  "Midrange Systems Technical

             midrange-l-bounce         Discussion"

             s@xxxxxxxxxxxx            <midrange-l@xxxxxxxxxxxx>


cc


             05/02/2006 11:34
Subject
             AM                        RE: DASD arm worksheets





             Please respond to

             Midrange Systems

                 Technical

                Discussion

             <midrange-l@midra

                 nge.com>









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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