Messages in this thread | | | Date | Thu, 12 Jun 2008 15:08:48 -0400 | From | Bill Davidsen <> | Subject | Re: Linux MD RAID 5 Benchmarks Across (3 to 10) 300 Gigabyte Veliciraptors |
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Justin Piszcz wrote: > > > On Wed, 11 Jun 2008, Justin Piszcz wrote: > >> >> >> On Wed, 11 Jun 2008, Bill Davidsen wrote: >> >>> Justin Piszcz wrote: >>>> First, the original benchmarks with 6-SATA drives with fixed >>>> formatting, using >>>> right justification and the same decimal point precision throughout: >>>> http://home.comcast.net/~jpiszcz/20080607/raid-benchmarks-decimal-fix-and-right-justified/disks.html >>>> Now for for veliciraptors! Ever wonder what kind of speed is >>>> possible with >>>> 3 disk, 4,5,6,7,8,9,10-disk RAID5s? I ran a loop to find out, each >>>> run is >>>> executed three times and the average is taken of all three runs per >>>> each RAID5 disk set. >>>> >>>> In short? The 965 no longer does justice with faster drives, a new >>>> chipset >>>> and motherboard are needed. After reading or writing to 4-5 >>>> veliciraptors >>>> it saturates the bus/965 chipset. >>> >>> This is very interesting, but a 16GB chunk size bears no >>> relationship to anything I would run in the real world, and I >>> suspect most people are in the same category. >> >> I based my bonnie++ test on: >> http://everything2.org/?node_id=1479435 >> >> So I could compare to his results. >> >> I use a 1024k (1MiB) with 16384 stripe, this offered the best overall >> read/write/rewrite performance AFAIK. > > 1024k chunk size (raid5 chunk size) > echo 16384 > stripe_cache_size
Please don't explain any more, I'm confused enough already. I can't make those numbers match 16G no matter how I add them, either the contents of the column labeled "size:chunk size" isn't the size of the chunk, or you have a multiplier floating around that I don't see. And you eliminated the degraded performance, since your stripe_cache_size is less than (raid5 chunk size)*(#disks), I would expect the reads in degraded mode to be dog slow because the don't fit in cache, even if 1024k is what I call chunk size and certainly not if chunk size is 16G.
-- Bill Davidsen <davidsen@tmr.com> "Woe unto the statesman who makes war without a reason that will still be valid when the war is over..." Otto von Bismark
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