On Tuesday November 3, laurent.corbes@xxxxxxxxxxxx wrote: > > What is really strange is that from all the tests I did the raw md perfs never > dropped. only a few MB of diff between kernel (~2%). This is maybe related to > the way upper FS write datas on the md layer. That isn't all that strange. It just says that the problem isn't with MD, but is in some other part of Linux closer to the filesystem. I did some tests with a range of kernels (all 'mainline', not the 'stable' versions that you used) and while I do see a noticeable dip at 2.6.30 (except with ext3) is see improved performance in 2.6.31 and even greater improvements with 2.6.32-rc5. So while I confirm that 2.6.30 is worse than earlier kernels, and that there was a general decline leading to that point, things have become dramatically better. So I don't think it is worth exploring very deeply. All the numbers in the graph come from 'bonnie' over the various file-systems on a 5-drive RAID6. NeilBrown
