I could be wrong, but my understanding is that the perc cards have BB write caches and that the SAS cards do not, which would certainly have a very significant effect in iops.
--M On Jan 22, 2010, at 4:38 PM, Kaerka Phillips wrote: > Hello, > > I was wondering if anyone on the linux-poweredge list has done any > performance testing of same or similar hardware using the PERC6 vs. the SAS6 > controller cards? I have 7 R805's, two of which have PERC6/i cards > installed, and the other 5 have SAS6/iR cards installed. I've been working > on diagnosing a performance problem on two of those with the SAS cards, and > have now discovered that every R805 with the SAS cards has similar levels of > poor local disk i/o performance. The R805's with PERC6 cards are similar in > performance level to our R905's with PERC6's, and a little better than our > 2950's with PERC5's. > > I can provide my stats, but since they're somewhat extensive, the short > answer is that the R805's which have PERC6 cards perform in the 16k to 30k > i/o per second, depending on write or read type with iozone; but the ones > with the SAS cards can barely do 1000 i/o's per second. These R805's are > similar, but not identical though, here is the mix below. > > All are RHEL5.4, 64bit, and the bottom 3 run kernel-xen, the top two are the > standard RHEL5 64bit kernel > 2x R805's with 2x cpu, 8gb ram, SAS6/iR card, 2x sas 3gbps disks, raid-1 - > Avg. 284 i/o per second > 3x R805's with 2x cpu, 64gb ram, SAS6/iR card, 2x sas 3gbps disks, raid-1 - > Avg. 687 i/o per second > 2x R805's with 2x cpu, 64gb ram, PERC6/i card, 2x sas 3gbps disks, raid-1 - > Avg. 26k i/o per second > > I'm hoping that someone else out there has done some other similar > performance testing, and can either tell me what I'm doing wrong or also show > similar results? My test methods have been using iozone, dd, and rsync. > (iozone command line: iozone -s 1m -r 16 -i 0 -i 2 -I -O -t 75) > > Thanks, > > KBP > _______________________________________________ > Linux-PowerEdge mailing list > [email protected] > https://lists.us.dell.com/mailman/listinfo/linux-poweredge > Please read the FAQ at http://lists.us.dell.com/faq _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
