On Mon, May 16, 2011 at 12:23:13PM -0400, Jeff wrote: > On May 16, 2011, at 9:17 AM, John Rouillard wrote: > >However, in my case I have an 8 disk raid 10 with a read only load (in > >this testing configuration). Shouldn't I expect more iops than a > >single disk can provide? Maybe pgiosim is hitting some other boundary > >than just i/o? > > > > given your command line you are only running a single thread - use > the -t argument to add more threads and that'll increase > concurrency. a single process can only process so much at once and > with multiple threads requesting different things the drive will > actually be able to respond faster since it will have more work to > do. > I tend to test various levels - usually a single (-t 1 - the > default) to get a base line, then -t (drives / 2), -t (#drives) up > to probably 4x drives (you'll see iops level off). Ok cool. I'll try that. > >Also it turns out that pgiosim can only handle 64 files. I haven't > >checked to see if this is a compile time changable item or not. > > that is a #define in pgiosim.c So which is a better test, modifying the #define to allow specifying 200-300 1GB files, or using 64 files but increasing the size of my files to 2-3GB for a total bytes in the file two or three times the memory in my server (96GB)? > also, are you running the latest pgiosim from pgfoundry? yup version 0.5 from the foundry. > the -w param to pgiosim has it rewrite blocks out as it runs. (it is > a percentage). Yup, I was running with that and getting low enough numbers, that I switched to pure read tests. It looks like I just need multiple threads so I can have multiple reads/writes in flight at the same time. -- -- rouilj John Rouillard System Administrator Renesys Corporation 603-244-9084 (cell) 603-643-9300 x 111 -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
