> > http://www.perfassoc.com/jsc/pdf/papers/flex-es_io_performance_02.pdf > > zSeries emulation on Intel maps ECKD onto open systems formatted DASD. It can be blindingly > > fast.
> Although your CPU performance in emulation, um, isn't. Very true in many instances. But down at the bottom end - VM/VSE land - I/O content of workloads is two and a half or so times more than with z/OS workloads. Roughly 65 Intel MHz per one z/Series MIPS - so a 3.2 GHz xSeries system is around 50 MIPS. Enough for most of the purposes outlined below. > I frankly don't see why you'd want to run z/Linux on a Flex-ES box. Oh, there are some good reasons. > If what you need is a cheap S/390 for development or for proving that your > app works once ported, use Hercules: since it's z/Linux you don't have > licensing concerns if you run it under Hercules, and you've saved > yourself a big whack of money right there. Absolutely. > If you care about > performance and this is a production app rather than a development box, > then emulating the S/390 is silly (it's not like you have legacy > Linux/390 code that ran on your 3090, you know): just put the app on the > native Linux for whichever platform, probably Intel, you have. Also true. However - what are the purposes for which z/Linux is being promoted? Linux will beat z/Linux in bang-for-buck on every other platform it supports. So the reason for z/Linux must be to access z/OS functionality in the same system. Very often it's to front-end a z/OS database server. z/Linux does the web serving bit, and DB2 on z/OS does the database bit. In this context, the PWD z/OS development system (z/OS free of charge subject to terms and conditions) coupled with a z/Linux distro makes a great deal of sense for proof of concept, pre-pilot, development, regression testing, demonstration and training purposes. Sure, the Linux performance is crap compared with other platforms - but the functionality of the combination of z/Linux and z/OS is what you're after. You can't do that on Hercules because IBM won't license z/OS to it. And you can't do it on native Intel because z/OS don't run there. I agree that to go near production with something like that would be insane. -- Phil Payne http://www.isham-research.com +44 7785 302 803
