changing stripe cache size
From: Linux Raid Study <hidden>
Date: 2009-09-17 01:30:58
Ok...I figured out...the max stripe_cache_size on my system is 8k. Since I was setting it to 32k, it was failing and staying at 1k. Per mdadm, my chunk size is default 64k. The final goal here is to export this /dev/md0 device to iSCSI initiators (running on different PCs) and measure performance. So, ques is what would be an optimal block size for iSCSI reads if chunk size is 64k and stripe cache size is 8k. Thanks for your help... 2009/9/16 Linux Raid Study [off-list ref]:
Hi: I tried to change the Raid5 stripe cache size by doing "echo 262144 > /sys/block/md0/md/stripe_cache_size" But if I do "cat /sys/block/md0/md/stripe_cache_size", it still shows 1024! Can someone please suggest how to increase stripe cache size? thanks! 2009/9/10 Keld Jørn Simonsen [off-list ref]:quoted
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:quoted
I build/compile my own kernel.. Have you done any benchmarks for Read RAID5 perf? Thanks! On 9/9/09, Majed B. [off-list ref] wrote:quoted
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[off-list ref] 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. [off-list ref] 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[off-list ref] 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@vger.kernel.org >> > 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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