Re: Raid5 Read Perf drop in 2.6.27

["Keld Jørn Simonsen" <keld@dkuug.dk>]

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. <majedb@gmail.com> 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-<version>
> >
> >  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<linuxraid.study@gmail.com> 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. <majedb@gmail.com> 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<linuxraid.study@gmail.com> 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.
> >
> --
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