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@xxxxxxxxx> 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@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Majed B. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
