Did you compare both kernel's config files to see whether these kernels have been compiled with different options? On Wed, Sep 16, 2009 at 10:57 AM, Linux Raid Study <linuxraid.study@xxxxxxxxx> wrote: > Hi Majed, All: > > I'm using the default scheduler with 2.6.21 and 2.6.27...do you know > if there is any difference? > > I rechecked the perf today - everything (i.e. disks, disk controller > etc) remaining the same, I see around 45MB/s difference in performance > when I change kernel from 2.6.21 to 2.6.27. I issue following cmd to > see performance: > hdparm -t /dev/md0 > > FYI...I'm using Seagate HDDs (7200 RPM) with RocketRaid 2310 controller. > > Any ideas...I have tried blockdev readahead option and it helps but > still not enough... > > Thanks a lot! > > On Wed, Sep 9, 2009 at 4:52 PM, Majed B. <majedb@xxxxxxxxx> 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@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. >> > -- 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
