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@xxxxxxxxx> 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@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
