chrism at imntv.com wrote: > Bowie Bailey wrote: > > Joshua Baker-LePain wrote: > > > On Thu, 12 Oct 2006 at 4:22pm, Bowie Bailey wrote > > > > > > > I have two identical servers. The only difference is that the > > > > first one has Maxtor 250G drives and the second one has Seagate > > > > 320G drives. > > > > > > > > OS: CentOS-4.4 (fully patched) > > > > CPU: dual Opteron 280 > > > > Memory: 16GB > > > > Raid card: 3ware 9550Sx-8LP > > > > Raid volume: 4-disk Raid 5 with NCQ and Write Cache enabled > > > > > > > > On the first server I have decent performance. Nothing > > > > spectacular, but good enough. The second one has about 1/3 the > > > > write speed. I can't find any difference between the systems. > > > > Both of them have the same stripe size, both have ext3 > > > > filesystems, both have write caching and NCQ turned on. I have > > > > already increased the read ahead setting to 16384 on both > > > > servers. > > > Turn off NCQ. Last I knew, this was still 3ware's recommendation. > > > > I can try that, but when I tested on the first server, I found that > > disabling NCQ increased the read performance by 10M/s and decreased > > the write performance by 10M/s. Maybe I'll get different results > > from the Seagate drives. > > Here's what I'm getting from a dual Opteron 275 box, Centos 4.4-64bit, > 2gb RAM and an 8 drive array of 750gig Seagates: > > 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 > localhost.locald 4G 248901 96 138957 40 308874 > 42 625.8 > > I've been applying all the various tricks that came up during the last > couple of threads. Turning NCQ off definitely made a big difference > for me. With NCQ off, I get these results: 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 Second 50G 20853 8 41899 11 192713 23 116.9 1 Write performance increased by 2M/s and read performance decreased by 2M/s. What tweaks have you applied so far? I would expect a 4-drive array to be slower than an 8-drive array, but not this much! -- Bowie