From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: ATA 4 KiB sector issues. Date: Tue, 9 Mar 2010 22:15:23 +1100 Message-ID: <20100309111523.GL28189@discord.disaster> 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: Karel Zak , 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: > > I did almost all my tests with scsi_debug or MD RAID0 on scsi_debug. > > It works as expected. > > Actually, for raid0, the alignment is questionable. Should it be a > multiple of chunk size or whole stripe size? I'm not sure, both ways > has bad and good sides.. But if it is the latter, the same issues > pops up again: do a 3-disk raid0 and you'll have to align to 3*2^N. Yes, alignment is still needed, especially for filesystems that can do stripe unit aligned allocation like XFS. If you don't align the filesystem properly, all the data IO will be mis-aligned to the underlying disks and stripe unit sized IO will hit multiple disks rather than just one.... Cheers, Dave. -- Dave Chinner david@fromorbit.com