Yeah, we've also seen performance issues with raid5 on the 9500 series products. The benchmarks we run look good, but when we've put them into production file server environments, the performance has been disappointing. With 500GB disks now available for $4.95 down at the local Walgreen's, we've gone to raid 1 and are _very_ pleased with the performance. Although it's been discouraged on this list, we're using xfs and the unsupported CentOS kernels and haven't had any problems. We're anxiously waiting the 'new, improved' xfs drivers for CentOS :) :)
The 9550 has better performance over the 9500, but I don't have any real numbers to back up the differences.
-- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety'' Benjamin Franklin 1775