This isn't all that surprising. The main weaknesses of RAID-5 are poor write performance and stupid hardware controllers that make the write performance even worse than it needs to be. Your numbers bear that out. Reads off RAID-5 are usually pretty good. Your 'dd' test is going to be a little misleading though. Most DB access isn't usually purely sequential; while it's easy to see why HW RAID-5 might outperform HW-RAID-10 in large sequential reads (the RAID controller would need to be smarter than most to make RAID-10 as fast as RAID-5), I would expect that HW RAID-5 and RAID-10 random reads would be about equal or else maybe give a slight edge to RAID-10. -- Mark Lewis On Fri, 2006-07-28 at 13:31 -0400, Jeff Trout wrote: > I too have a DL385 with a single DC Opteron 270. > It claims to have a smart array 6i controller and over the last > couple of days I've been runnign some tests on it, which have been > yielding some suprising results. > > I've got 6 10k U320 disks in it. 2 are in a mirror set. We'll not > pay any attention to them. > The remaining 4 disks I've been toying with to see what config works > best, using hardware raid and software raid. > > system info: > dl dl385 - 1 opteron 270 - 5GB ram - smart array 6i > cciss0: HP Smart Array 6i Controller > Firmware Version: 2.58 > Linux db03 2.6.17-1.2157_FC5 #1 SMP Tue Jul 11 22:53:56 EDT 2006 > x86_64 x86_64 x86_64 GNU/Linux > using xfs > > Each drive can sustain 80MB/sec read (dd, straight off device) > > So here are the results I have so far. (averaged) > > > hardware raid 5: > dd - write 20GB file - 48MB/sec > dd - read 20GB file - 247MB/sec > [ didn't do a bonnie run on this yet ] > pretty terrible write performance. good read. > > hardware raid 10 > dd - write 20GB - 104MB/sec > dd - read 20GB - 196MB/sec > bonnie++ > Version 1.03 ------Sequential Output------ --Sequential Input- > --Random- > -Per Chr- --Block-- -Rewrite- -Per Chr- -- > Block-- --Seeks-- > Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec % > CP /sec %CP > db03 9592M 45830 97 129501 31 62981 14 48524 99 185818 > 19 949.0 1 > > software raid 5 > dd - write 20gb - 85MB/sec > dd - read 20gb - 135MB/sec > > I was very suprised at those results. I was sort of expecting it to > smoke the hardware. I repeated the test many times, and kept getting > these numbers. > > bonnie++: > Version 1.03 ------Sequential Output------ --Sequential Input- > --Random- > -Per Chr- --Block-- -Rewrite- -Per Chr- -- > Block-- --Seeks-- > Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec % > CP /sec %CP > db03 9592M 44110 97 81481 23 34604 10 44495 95 157063 > 28 919.3 1 > > software 10: > dd - write - 20GB - 108MB/sec > dd - read - 20GB - 86MB/sec(!!!! WTF? - this is repeatable!!) > bonnie++ > Version 1.03 ------Sequential Output------ --Sequential Input- > --Random- > -Per Chr- --Block-- -Rewrite- -Per Chr- -- > Block-- --Seeks-- > Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec % > CP /sec %CP > db03 9592M 44539 98 105444 20 34127 8 39830 83 100374 > 10 1072 1 > > > so I'm going to be going with hw r5, which went against what I > thought going in - read perf is more important for my usage than write. > > I'm still not sure about that software 10 read number. something is > not right there... > > -- > Jeff Trout <jeff@xxxxxxxxxxxxx> > http://www.dellsmartexitin.com/ > http://www.stuarthamm.net/ > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match
