From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: increasing stripe_cache_size decreases RAID-6 read throughput Date: Wed, 28 Apr 2010 07:24:19 +1000 Message-ID: <20100428072419.22779335@notabene.brown> References: <20100427164126.2765f9e0@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Joe Williams Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, 27 Apr 2010 10:18:36 -0700 Joe Williams wrote: > On Mon, Apr 26, 2010 at 11:41 PM, Neil Brown wrote: > > On Sat, 24 Apr 2010 16:36:20 -0700 Joe Williams wrote: > > > > The whole 'queue' directory really shouldn't appear for md devices but for > > some very boring reasons it does. > > But read_ahead for md0 is in the queue directory: > > /sys/block/md0/queue/read_ahead_kb True - but it shouldn't be. read_ahead has nothing to do with the queue. /sys/block/md0/bdi/read_ahead_kb is (in my mind) the more natural way to access that information. Actually it should be /sys/class/block/md0/bdi/read_ahead_kb but that is a little off-topic. > > I know you said read_ahead is irrelevant for the individual disk > devices like sdb, but I thought it was implied the read_ahead for md0 > is significant. > NeilBrown