From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Evans Subject: Re: Alignment of RAID on specific boundary Date: Mon, 4 Jan 2010 22:57:48 -0800 Message-ID: <4877c76c1001042257h49103054t977de11410eb65c6@mail.gmail.com> References: <7b3edae11001041130n42d053fcpc4923b22278c5671@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: <7b3edae11001041130n42d053fcpc4923b22278c5671@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Khelben Blackstaff Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, Jan 4, 2010 at 11:30 AM, Khelben Blackstaff wrote: He's using SDDs with 128KByte erase blocks. > Is there a way to make the RAID data start at a particular offset ? > (In my case 512 sectors) ? > > Thank you for your time. > -- You want the RAID data chunks aligned so that they start on a 512byte sector address that fulfills (sector & 0xFF) == 0. As far as I am aware, using metadata 0.90 OR 1.0 will start the actual data at the beginning of the partition, reserve some space near the end, and use the very end for the metadata. Format 1.1 will reserve the space at the beginning, and I have just checked; 00000400 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00003000 (LVM2 header) It starts the LVM2 header after 0x3000 bytes (64K chunk size); I'd hope to see it around 0x10000. It looks like the data isn't padded up to the desired offset. I agree, it would be useful to have an option to specify the offset of the first data chunk.