From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karel Zak Subject: Re: ATA 4 KiB sector issues. Date: Tue, 9 Mar 2010 12:50:18 +0100 Message-ID: <20100309115017.GF18077@nb.net.home> References: <4B947393.2050002@kernel.org> <170fa0d21003081134g491034e5v4aad4d43853e48ec@mail.gmail.com> <4B95F071.3070400@msgid.tls.msk.ru> <20100309100153.GD18077@nb.net.home> <4B961FE1.5040105@msgid.tls.msk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4B961FE1.5040105@msgid.tls.msk.ru> Sender: linux-kernel-owner@vger.kernel.org To: Michael Tokarev Cc: Mike Snitzer , "Martin K. Petersen" , Tejun Heo , "linux-ide@vger.kernel.org" , lkml , Daniel Taylor , Jeff Garzik , Mark Lord , tytso@mit.edu, "H. Peter Anvin" , hirofumi@mail.parknet.co.jp, Andrew Morton , Alan Cox , irtiger@gmail.com, Matthew Wilcox , aschnell@suse.de, knikanth@suse.de, jdelvare@suse.de, Jim Meyering , Neil Brown List-Id: linux-ide@vger.kernel.org On Tue, Mar 09, 2010 at 01:16:01PM +0300, Michael Tokarev wrote: > Karel Zak wrote: > > # mdadm --create /dev/md8 --level=5 --raid-devices=4 /dev/sdb{1,2,3,4} > > That's 3-disk stripe size with default 64Kb chunk size, which makes > 3x64=320KiB - the number to which everything should be aligned. > > > # fdisk -lcu /dev/md8 > > > > Disk /dev/md8: 1572 MB, 1572667392 bytes > > 2 heads, 4 sectors/track, 383952 cylinders, total 3071616 sectors > > Units = sectors of 1 * 512 = 512 bytes > > Sector size (logical/physical): 512 bytes / 4096 bytes > > I/O size (minimum/optimal): 65536 bytes / 65536 bytes > > And here we go: fdisk does not see the right number: nothing > is dividable by 3. > > [] > > # cat /sys/block/md8/md8p{1,2}/alignment_offset > > 0 > > 0 > > And that's where the issue is. md does not {sup,re}port all > this stuff yet. > > This is what I'm talking about. Note that I have 2.6.31.12-174.2.22.fc12.x86_64 kernel on my laptop. It would be better for serious tests to use 2.6.33. Karel -- Karel Zak