I would expect that some would challenge your conclusion based on the idea that the MP effect does not even appear unless you are running at or near capacity. If I have two cpus or IFLs and 1.1 cpu's worth of demand, will I notice the MP effect? Probably not. I probably will see a better service level than when I was trying to service the same demand with only 1 cpu. The question is, if n tasks causes a single engine to run at 100%, will 2 engines be able to service 2n tasks as well as 1 serviced n? I think that under normal circumstances, the answer is that the 2 engine machine will only be able to service somewhat less than 2n.
Regards, Richard Schuh > -----Original Message----- > From: The IBM z/VM Operating System > [mailto:ib...@listserv.uark.edu] On Behalf Of Barton Robinson > Sent: Tuesday, February 03, 2009 10:57 AM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: Correcting Statements From Marketing > > Ok here's some heresy that I've presented to IBM and maybe > was communicated to their sales folks. From a capacity > planning and service level perspective, adding a CPU gives > you MORE than 100%, not less than. > Really, BUT ONLY if you actually care about service levels. > > From a service level perspective, i know that i can provide > on ONE IFL a given service at 80% CPU utilization. If I ADD > an IFL, and more work of a similar nature, I now have TWO > IFLs, and I know that I can provide that SAME service at 180% > CPU Util. > > So, I went from ONE IFL, to TWO IFLs, and increased my target > CPU utilization by 1.25 times. > > On z/OS if you just run at 100% all the time, and run batch > to soak up cycles, then add a CPU and you don't get 100% of > one CPU more work done. > That is the only time MP factors should matter. > > And this heresy is why it is much easier to deal with > installations running multiple IFLs, because the performance > will be better at higher utilizations than single IFLs at > lower utilizations. Adding a second IFL more than doubles > your usable capacity. Adding a 3rd or 4th is less dramatic. > > From a historical perspective, we used to have the MASTER > PROCESSOR effect where adding a CPU added much less capacity. > Installations today do not see this impact. > > > Schuh, Richard wrote: > > This got no response when posted under a different topic: > > > > "Yikes, We have someone from IBM Marketing now making the > statement, > > "I have confirmed...no MP factor with IFLs....". That is the entire > > statement, all of the dots included. I did not replace > anything with > > ellipses. Somehow, that does not ring true. I mentioned that the > > rating of an IFL is the same as that of an ordinary CPU and someone > > went to marketing for "the real answer". Perhaps they should have > > said, "No different MP factor for IFLs than for regular > CPUs, they are > > the same in that regard." That would make more sense. > Anyone from IBM > > care to comment - you will probably be quoted." > > > > I am not considered an authority on the topic, especially when I > > disagree with an interpretation of a statement made by IBM > marketing. > > I need to disabuse someone of their notion because it will > affect the > > capacity planning process. They do not seem to believe that running > > the same O/S on two systems, one with n standard CPUs and the other > > with the same number of IFLs will produce a result of equal > MP effect. > > > > Barton, you are also invited to respond. At least one of > the people on > > the other side of the fence will take your word for it. > > > > Regards, > > Richard Schuh > > > > >
