From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: Striping does not increase performance. Date: Mon, 12 Mar 2012 16:23:21 +0000 Message-ID: <4F5E22F9.1040208@anonymous.org.uk> References: <20120312125720.GL4558@voyageur.mas.nom.fr> <20120312135847.GM4558@voyageur.mas.nom.fr> <4F5E0963.6080708@cesnet.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F5E0963.6080708@cesnet.cz> Sender: linux-raid-owner@vger.kernel.org To: Jiri Horky Cc: Erwan MAS , Caspar Smit , linux-raid@vger.kernel.org, fio@vger.kernel.org List-Id: linux-raid.ids On 12/03/2012 14:34, Jiri Horky wrote: > Hi, > > as for alignment, please also check md metadata format version (-e > switch of mdadm). The version that ensures alignment is 1.0, which > places the metadata information to the back of the drive. As far as I can tell from looking at the source, ever since the 1.x metadata types were introduced (with mdadm 2.0, in August 2005): * the data offset on 1.1 and 1.2 arrays has always been 4K-aligned, * the superblock offset for 1.0 arrays has always been 4K-aligned, * the bitmap offset for all 1.x arrays has always been 4K-aligned. As of mdadm 3.1.2 (March 2010), the data offset for new 1.1 and 1.2 arrays is always 1MB (2048 sectors), so they're also 1M-aligned. Cheers, John.