On Wed, Jun 10, 2015 at 11:02 PM, Ming Lin <mlin@xxxxxxxxxx> wrote: > On Wed, Jun 10, 2015 at 10:39 PM, Markus Stockhausen > <stockhausen@xxxxxxxxxxx> wrote: >>> Von: linux-raid-owner@xxxxxxxxxxxxxxx [linux-raid-owner@xxxxxxxxxxxxxxx]" im Auftrag von "Roman Mamedov [rm@xxxxxxxxxxx] >>> Gesendet: Donnerstag, 11. Juni 2015 02:27 >>> An: Ming Lin >>> Cc: linux-raid@xxxxxxxxxxxxxxx; Neil Brown >>> Betreff: Re: write performance of HW RAID VS MD RAID >>> >>> On Wed, 10 Jun 2015 15:27:07 -0700 >>> Ming Lin <mlin@xxxxxxxxxx> wrote: >>> >>> > Hi NeilBrown, >>> > >>> > As you may already see, I run a lot of tests with 10 HDDs for the patchset >>> > "simplify block layer based on immutable biovecs" >>> > >>> > Here is the summary. >>> > http://minggr.net/pub/20150608/fio_results/summary.log >>> > >>> > MD RAID6 read performance is OK. >>> > But write performance is much lower than HW RAID6. >>> > >>> > Is it a known issue? >>> >>> Did you tune the stripe_cache_size for the array? Try 32768. >>> https://peterkieser.com/2009/11/29/raid-mdraid-stripe_cache_size-vs-write-transfer/ >> >> +1 for giving an increased cache size a try. > > Will try it. > >> >> From the numbers I anticipate that you are doing sequential >> read/write tests. Otherwise I would expect a write penalty for >> the HW RAID setup too. > > Yes, > > [global] > ioengine=libaio > iodepth=64 > direct=1 > runtime=1800 > time_based > group_reporting > numjobs=48 > gtod_reduce=0 > norandommap > write_iops_log=fs > > [job1] > bs=640K > directory=/mnt > size=5G > rw=write I tested xfs write for RAID6 stripe size 64k with different stripe_cache_size. stripe_cache_size throughput(MB/s) -------------------------- -------------------------- 256 181.7 512 185.1 768 178.3 1024 194.4 2048 227 4096 247 8192 300.3 16834 312.4 32768 304 While xfs write for HW RAID6 throughput is 753.16 MB/s -- 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
