Hello: According to Wiki at http://linux-raid.osdl.org/index.php/Performance, disabling NCQ helps in improving perf....I thought enabling command-queuing helps is perf improvement. Can someone pls elaborate how disabling NCQ helps.... I have 3 seagate HDDs (7200RPM) and 2 WD VelcoiRaptor (10k RPM) and disabling NCQ doesn't help in performance.... thanks! [ snip from wiki ] # Disable NCQ on all disks. (for raptors it increases the speed 30-40MiB/s) echo "Disabling NCQ on all disks..." for i in $DISKS do echo "Disabling NCQ on $i" echo 1 > /sys/block/"$i"/device/queue_depth done 2009/9/10 Keld Jørn Simonsen <keld@xxxxxxxx>: > 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@xxxxxxxxx> 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@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 > -- 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
