Re: 515 not performing to full rating due to disk arms? -- MIDRANGE-L

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From: Scott Lindstrom <SLindstrom@xxxxxxxxxx>
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Date: Thu, 12 Jun 2008 10:54:09 -0500
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<DIV>Ph=
illip - this is great info!  Do you have a link of the name/number of =
the redpaper you refer to so I can take a look at it?</DIV><DIV><FON=
T face=3D"Default Monospace,Courier New,Courier,monospace"> </D=
IV><DIV>Is i=
t this one?:</DIV><DIV>IBM System i Overview: Models 515, 525, 550, =
570, 595, and More</DIV><DIV> </DIV><DIV>from: Philipp Rusch - NewVision-IT <philipp=
.rusch@xxxxxxxxxxxxxxx> subject: Scott Lindstrom schrieb: >=
> Since you can only have 8 drives on a 515, the only constraint would<B=
R>>> have be memory. >> What are "they" recommending for a b=
ox ? >> What does this application do and what is the primary lang=
uage ? >>     > > Pat- > > The =
box is being quoted at 3gb of memory. The app is JD Edwards World > (=
English). > > If 3gb is not enough RAM to get the rated CPW, I =
wonder what is? > > The BP recommends an M25 series box. &gt=
; > Scott > >   Hello Scott, CPW Measures=
are ALWAYS meant for the system being fully equipped with every disk, m=
emory and cache controller you can put in. BUT: The i5-515 is a special =
one, as is the 510-M15. These machines are politically constrained, whic=
h means that you cannot use the full CPU-Power if you are running I/O in=
tensive jobs on them. The good news is, that there is no more "Hyper=
visor job" artificially contorlling how much power you can get. Ther=
e is a note in the Redpaper about these new systems an I think your BP i=
s referring to that: Note 1: The Model 515 provides full processor power=
(batch or 5250 OLTP) for applications that are not I/O intensive. For =
applications that are I/O intensive, this translates to approximately 80=
0 CPW (batch or 5250 OLTP) for either the 1-way or 2-way because the Mo=
del 515 has a maximum of eight disk drives. CPW is used to compare relat=
ive performance rating among processor models within the IBM System =
i family. As a reminder, do not use CPW as the sole metric for sizing wo=
rkloads on any IBM System i model. Additional considerations include<BR=

disk I/O-per-second rates and application workload attributes. As a st=

arting point for disk I/Os per second on the Model 515, consider a maxim=
um of approximately 115 disk I/Os per second. We recommend that you siz=
e a Model 515 workload using a sizing tool, such as the IBM Systems Work=
load Estimator, which you can access at the following address: </FON=
T><A href=3D"http://www.ibm.com/servers/eserver/iseries/perfmgmt/sizing.htm=
l" target=3D=5Fblank>http://www.ibm.com/servers/eserver/iseries/perfmgmt/sizing.html</F=
ONT></A> That said, it depends on what you do with your i5. It certainly runs Ja=
va or a WAS-instance a lot more faster than a model 800 with 800 CPW wou=
ld do. But don't expect it to run 5 times as fast with a "traditional" w=
orkload. Some numbers for comparison: The 515 maxes out at 16 GB memo=
ry with 533 MHz, 8x 70 GB 15k SCSI disks and two RAID controllers, one w=
ith 40MB and the other one with a 90 MB cache. The 520-M15/25 maxes =
out at 16 GB memory with 667MHz, 6x 70 GB 15k SAS disks (well it's not t=
hat easy: the load source shall be 70 GB, the other disks can be up =
to 283 GB per diskdrive, but then how to build a RAID5 ...) The SAS disk=
are a little faster than the SCSI ones, but you only got 6 arms in =
an M15. The M25 is allowed to be expanded beyond this with an EXP24 disk<BR=

addition for instance ... So the question is: how many user-license=

s do you need ? The 515 ends at 40 users, if you exceed this, you need a=
n M25, otherwise it makes no difference for me. </DIV><DIV=

</DIV>=