Hardware raid is not necessarily faster than software raid. If you are going to do raid5...make sure your card has plenty of cache. However, that may be moot anyway unless you use some filesystem other than ext3...is it a 3ware card? 3ware + RAID5 + ext3 = slow.
Well, I had them ship me a 3ware 9550 card, and yes, am using ext3, -there's no onboard battery backup module, so the write cache is disabled. So this would be slow then? Am using this as a Java Development machine.
Disabling write cache will slow you down big time if you have a lot of I/O. If you don't, it probably does not matter.
Any suggestions as to the filesystem type that would work best? I'll order a battery backup unit so we can proceed and enable write cache.
Since you are running 64-bit Centos, I guess using the plus kernel and the XFS filesystem should do you good. XFS has the best write performance and it sings on the 3ware.