From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: ATA 4 KiB sector issues. Date: Tue, 09 Mar 2010 14:38:57 +0300 Message-ID: <4B963351.50707@msgid.tls.msk.ru> 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> <20100309111523.GL28189@discord.disaster> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from isrv.corpit.ru ([81.13.33.159]:42171 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754592Ab0CILi7 (ORCPT ); Tue, 9 Mar 2010 06:38:59 -0500 In-Reply-To: <20100309111523.GL28189@discord.disaster> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Dave Chinner 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 Dave Chinner wrote: > 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.... I understand alignment is needed, the question is if the alignment should be to chunk size or full-stripe size. In neither case it will be bad for underlying disks. /mjt