From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: iostat with raid device... Date: Thu, 14 Apr 2011 07:00:11 +1000 Message-ID: <20110414070011.68691ab5@notabene.brown> References: <20110409094629.2eae2d5b@notabene.brown> <20110409085044.GB417@cthulhu.home.robinhill.me.uk> <20110411092559.GA20532@cthulhu.home.robinhill.me.uk> <20110411095355.GB20532@cthulhu.home.robinhill.me.uk> <20110411201808.47cd19d5@notabene.brown> <20110412125141.679baaf0@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Linux Raid Study Cc: Robin Hill , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Wed, 13 Apr 2011 11:21:52 -0700 Linux Raid Study wrote: > Let me reword previous email... >=20 > I tried to change stripe_cache_size as following and tried values > between 16 to 4096 > echo 512 > /sys/block/md0/md/stripe_cache_size >=20 > But, I'm not seeing too much difference in performance. I'm running o= n > 2.6.27sh kernel. I wouldn't expect much difference. >=20 > Any ideas... On what exactly? What exactly are you doing, what exactly are the results? What exactly= don't you understand? Detail help. NeilBrown >=20 > Thanks for your help... >=20 > On Tue, Apr 12, 2011 at 12:36 PM, Linux Raid Study > wrote: > > Hello Neil, > > > > For the benchmarking purpose, I've configured array of ~30GB. > > stripe_cache_size is 1024 (so 1M). > > > > BTW, I'm using Windows copy (robocopy) utility to test perf and I > > believe block size it uses is 32kB. But since everything gets writt= en > > thru VFS, I'm not sure how to change stripe_cache_size to get optim= al > > performance with this setup... > > > > Thanks. > > > > On Mon, Apr 11, 2011 at 7:51 PM, NeilBrown wrote: > >> On Mon, 11 Apr 2011 18:57:34 -0700 Linux Raid Study > >> wrote: > >> > >>> If I use --assume-clean in mdadm, I see performance is 10-15% low= er as > >>> compared to the case wherein this option is not specified. When I= run > >>> without --assume_clean, I wait until mdadm prints "recovery_done"= and > >>> then run IO benchmarks... > >>> > >>> Is perf drop expected? > >> > >> No. =A0And I cannot explain it.... unless the array is so tiny tha= t it all fits > >> in the stripe cache (typically about 1Meg). > >> > >> There really should be no difference. > >> > >> NeilBrown > >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html