Hi guys, First of all thanks for the replies... I will be back at work on Sunday... I will try the benchmark tools and send you data from z/VM and Linux.
Thanks again! Offer Baruch On Wed, Aug 5, 2009 at 9:50 AM, Rob van der Heij < [email protected]> wrote: > 2009/8/4 עופר ברוך <[email protected]>: > > > Any thoughts? > > Is my test case ok? Am I doing something wrong? > > Is this normal behavior? > > If you're able to collect raw monitor data from z/VM, that should tell > us whether there were any issues outside Linux that can explain it. > We're happy to look into the data for you. Send me a note off-list for > details. > > For inside Linux, we'd need Linux metrics too. My experience with > measuring disk I/O in Linux is that normally the large difference can > be explained because one of the cases did not actually do I/O (or not > as much as the other). For example, when you have enough memory > compared to the data set (like your 300 MB in 1G) and the test runs > shorter than 30 seconds, there is no I/O at all (at least not before > the dd command completes). In that case you're doing a CPU measurement > and your limithard may be impacting your results. > > Re: expecting great I/O performance: We don't make the disks spin > faster. Your DASD subsystem is made up of simple consumer quality disk > drives (well, 15K drives are not as bad as the 4800 drives you put in > your netbook). Once you actually write to disk, that will be equally > slow. Though you 300 MB/s will nicely go into NVS and be written out > later... > Mainframe I/O performance shines in that you do things in parallel, > that does not mean that without things in parallel something will run > faster (and empty bus does not drive 50 times as fast as one filled > with passengers). > > Rob > -- > Rob van der Heij > Velocity Software > http://www.velocitysoftware.com/ > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or > visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
