From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: Awful Raid10,f2 performance Date: Mon, 02 Jun 2008 16:53:07 +0200 Message-ID: <48440953.3040004@wpkg.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Jon Nelson Cc: Linux-Raid List-Id: linux-raid.ids Jon Nelson schrieb: > I have set up a 3-disk raid10 using f2 layout using 3x SATA disks each > capable of 70+ MB/s (give or take). > The CPU is a dual core 64 bit Athlon 3600+, and the SATA interface > consists of NVidia MCP55+ (PCIe or whatever). > Previously this was a 3 disk raid5. > The problem: I'm getting really awful transfer rates. 7-9MB/s > per-drive with 21-30MB/s combined. The average hangs around 22-24MB/s. > This, I feel, is really awful! > > What parameters can I twiddle to improve the performance? > I am not using NCQ. > The drives individually are capable of 70+ MB/s. > I am using the deadline I/O scheduler but I have tried the others. > This is the openSUSE 2.6.22.17 kernel. > I am getting the I/O rates via dstat. > I am using the jfs filesystem primarily. > The operation I am performing varies but the I/O rates don't (much). > In particular, moving one 17G file from a logical volume (I am using > LVM) to another, both filesytems are JFS. > The load is around 2.6, with these four processing being the top CPU > consumers (they wiggle around a bit): > > > 2034 root 10 -5 0 0 0 D 10 0.0 201:00.30 md0_raid10 > 10631 root 18 0 8436 1076 668 D 7 0.1 2:07.65 mv > 218 root 15 0 0 0 0 D 3 0.0 2:06.30 pdflush > 2182 root 10 -5 0 0 0 S 3 0.0 0:32.51 jfsCommit > > Is there more information that I can provide that can help explain why > I'm getting such slow speeds? It would be interesting to know the raw values of your RAID-10 (without any filesystem). I.e. # dd if=/dev/zero of=/dev/md10 bs=64k count=10000 # echo 3 > /proc/sys/vm/drop_caches # dd if=/dev/md10 of=/dev/null bs=64k -- Tomasz Chmielewski http://wpkg.org