From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Nelson Subject: unbelievably bad performance: 2.6.27.37 and raid6 Date: Sat, 31 Oct 2009 10:55:50 -0500 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: Sender: linux-raid-owner@vger.kernel.org To: LinuxRaid List-Id: linux-raid.ids I have a 4 disk raid6. The disks are individually capable of (at least) 75MB/s on average. The raid6 looks like this: md0 : active raid6 sda4[0] sdc4[5] sdd4[4] sdb4[6] 613409536 blocks super 1.1 level 6, 64k chunk, algorithm 2 [4/4] [UUUU] The raid serves basically as an lvm physical volume. While rsyncing a file from an ext3 filesystem to a jfs filesystem, I am observing speeds in the 10-15MB/s range. That seems really really slow. Using vmstat, I see similar numbers (I'm averaging a bit, I'll see lows of 6MB/s and highs of 18-20MB/s, but these are infrequent.) The system is, for the most part, otherwise unloaded. I looked at stripe_cache_size and increased it to 384 - no difference. blockdev --getra reports 256 for all involved raid components. I'm using the deadline I/O scheduler. Am I crazy? Is 12.5MB/s (average) what I should expect, here? What might I look at here? -- Jon