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. > -- 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
