Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Leroy, drbd folks, After a while of collecting and profiling my systems i discovered that our poor performance problems were not related of processor, raid controller or kernel configuration. It's all about raid5/6 level configurations that is absolutely unreliable. In details reading and writing directly to the raid disk, with an ext3 partition for example, gives more than 200 mbyte/sec with await and svc time of approx 1.2 ms versus reading and writing with drbd (either syncing or live i/o) gives extremely poor performance (i got 30-40 mbyte/sec with 3ware 9650-8p configured in raid6 and i have 20 mbytes/sec with Compaq Smart Array p400 configured in raid5 mode. In both raid5/6 configurations, i/o seems stucked as i've reported in my previous post with very high iowait values (await up to 5000 ms, svctime up to 1000 ms) Switching to raid0 / raid10 configurations, totally solved our problems. Sync its up to 200mbyte/sec, live i/o seems good as well but i'm still testing the vmware infrastructure... If anyone has any idea of what's going on.... Thanks -- So long and thank for all the fish -- #Matteo Tescione #RMnet srl Il 7-11-2007 16:26, "Leroy van Logchem" <leroy.vanlogchem at wldelft.nl> ha scritto: > Matteo wrote: >> Hi Lars and thank for your quick answer, i had a little look at the kernel >> Changelog and i saw they changed sg_set_page, suggestin use of >> sg_assign_page.I went to drbd/drbd_worker.c changin sg_set_page to >> sg_assign_page and it >> compiles without problems. So i solved the oops usin the rc2... >> >> BUT, even switching to new kernel my problems remains the same... >> I have tested latest drbd/kernel with CORE2/QUAD processors and i'm in deep >> troubles, syncer get stuck at 20mb/s with incredible high await/iowait times: >> > You might want to instrument the kernel and use oprofile. > > URL : http://oprofile.sf.net > Summary : System wide profiler > Description : > Profiling runs transparently during the background, and profile data > can be collected at any time. oprofile makes use of the hardware performance > counters provided on Intel P6, and AMD Athlon family processors, and can use > the RTC for profiling on other x86 processor types. > > Enable both Kernel profiling and debugging support. Oprofile needs the > uncompressed vmlinux. > > I don't know your distro but you can find some setup/use tips at: > http://www.linuxtopia.org/online_books/centos5/centos5_administration_guide/ce > ntos5_s1-oprofile-configuring.html > > Compare short benchmarks with cold caches using the P4 vs CORE2 with the > same kernel setup. Include /bin/sync after the benchmark. > > > > > > > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user >