From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: Raid5 Read Perf drop in 2.6.27 Date: Thu, 10 Sep 2009 19:22:19 +0200 Message-ID: <20090910172219.GB420@rap.rap.dk> References: <70ed7c3e0909091652m60b0ea9cp7000db919a639c35@mail.gmail.com> <70ed7c3e0909091827i745e2e38u6f8e246a0c9a49f@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Linux Raid Study Cc: "Majed B." , linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi There is some data on raid5 performance (and other raid types) at our wiki at: http://linux-raid.osdl.org/index.php/Performance When you have something you want to share with others, then we can add your info to the data there, either by a URL or by direct inclusion in the wiki. best regards keld On Wed, Sep 09, 2009 at 06:45:31PM -0700, Linux Raid Study wrote: > I build/compile my own kernel.. > > Have you done any benchmarks for Read RAID5 perf? > > Thanks! > > On 9/9/09, Majed B. wrote: > > Well, that's my point. To make sure that your kernels are identical in > > options, compare the .config files found in /usr/src/linux- > > > > You may find changes and differences in areas like bluetooth, > > wireless, ...etc. These don't matter. > > > > Did you compile your own kernel, or are you using one compiled for a > > specific distro? > > > > On Thu, Sep 10, 2009 at 4:17 AM, Linux Raid > > > > Study wrote: > > > Yes - the setup is the same. The only thing that changes is the kernel. > > > > > > I have 4 HDDs (2 from WD VelociRaptor 150GB/10k RPM and 2 from Seagate > > > 320GB/7.2k RPM). The HDDs are connected using two Silicon Image SATA > > > controllers (Sil3132) connected to my host using PCIe. > > > > > > I use the default kernel scheduling scheme. > > > > > > Thanks! > > > > > > On 9/9/09, Majed B. wrote: > > >> Are you sure you're using the same Kernel Scheduler on both kernels? > > >> > > >> Have you checked and verified that the same drivers are being loaded? > > >> (IDE vs. AHCI -- proprietary drivers vs. open source) > > >> > > >> This is interesting! > > >> > > >> > > >> On Thu, Sep 10, 2009 at 1:54 AM, Linux Raid > > >> Study wrote: > > >> > Hello: > > >> > > > >> > I'm benchmarking RAID5 Read performance with 4 disks and notice perf > > >> > drop when using kernel 2.6.27. > > >> > The perf with 2.6.27 is 150MB/s whereas with kernel 2.6.21 (and same > > >> > setup), the perf is 180MB/s/ > > >> > > > >> > > > >> > > > >> > Some of the tests I have done: > > >> > 1. I ran experiments using iozone also but notice that READ perf with > > >> > RAID5 in 2.6.27 is ~30% less as compared to 2.6.21. > > >> > Write perf is similar but Read is an issue. > > >> > > > >> > 2. On 2.6.27, I played around with chunk size and blocksize parameters > > >> > and got ~5% improvement but not much. I used following cmds: > > >> > > > >> > #mdadm --create /dev/md0 --level=5 --assume-clean --raid-devices=4 > > >> > /dev/sda /dev/sdb /dev/sdc /dev/sdd --chunk=32 > > >> > #mke2fs -b 4096 -E stride=8 /dev/md0 > > >> > > > >> > #time dd if=/dev/md0 of=/dev/null bs=94208 count=1024 > > >> > > > >> > > > >> > Is this perf drop a known issue? Can someone please recommend some > > >> > performance tuning tips? > > >> > > > >> > Thanks a lot for your time and help! > > >> > > >> > -- > > >> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > > >> > the body of a message to majordomo@vger.kernel.org > > >> > More majordomo info at http://vger.kernel.org/majordomo-info.html > > >> > > > >> > > >> > > >> > > >> -- > > >> > > >> Majed B. > > >> > > > > > > > > > > > > > -- > > > > Majed B. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html