From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raz Subject: Re: stripe_cache_size and performance Date: Fri, 22 Jun 2007 18:01:59 +0300 Message-ID: <5d96567b0706220801v76c1c19cl7448050e62e0860b@mail.gmail.com> References: <5d96567b0706211242p7f03bd1cw9102ae3e44d67cee@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: jnelson-linux-raid@jamponi.net Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 6/22/07, Jon Nelson wrote: > On Thu, 21 Jun 2007, Raz wrote: > > > What is your raid configuration ? > > Please note that the stripe_cache_size is acting as a bottle neck in some > > cases. > > Well, it's 3x SATA drives in raid5. 320G drives each, and I'm using a > 314G partition from each disk (the rest of the space is quiescent). what is the chunk size ?. Please note that a raid performance is dependent on the access pattern to the disks. What is this raid aimed to do ? more reads ? more writes ? If you can control the access pattern , you might be able to increase performance. > > On 6/21/07, Jon Nelson wrote: > > > > > > I've been futzing with stripe_cache_size on a 3x component raid5, > > > using 2.6.18.8-0.3-default on x86_64 (openSUSE 10.2). > > > > > > With the value set at 4096 I get pretty great write numbers. > > > 2048 and on down the write numbers slowly drop. > > > > > > However, at values above 512 the 'check' performance is terrible. By > > > 'check' performance I mean the value displayed by /proc/mdstat after > > > I issue: > > > > > > echo check > /sys/block/md0/md/sync_action > > > > > > When I say "terrible" I mean < 3MB/s. > > > When I use 384, the performance goes to ~70MB/s > > > 512.. 72-73MB/s > > > 640.. 73-74MB/s > > > > > > 768.. 3300 K/s. Wow! > > > > > > Can somebody 'splain to me what is going on? > > > > > > -- > > > Jon Nelson > > > - > > > 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 > > > > > > > > > -- > > Raz > > > > > > > > -- > Jon Nelson > - > 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 > -- Raz