From: Mike Mestnik Subject: Re: How to use mkfs.ext4 "stride=" on RAID correctly? Date: Wed, 13 Jan 2010 18:58:46 -0600 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: linux-ext4@vger.kernel.org Return-path: Received: from mail-ew0-f209.google.com ([209.85.219.209]:58557 "EHLO mail-ew0-f209.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043Ab0ANA6r convert rfc822-to-8bit (ORCPT ); Wed, 13 Jan 2010 19:58:47 -0500 Received: by ewy1 with SMTP id 1so316252ewy.28 for ; Wed, 13 Jan 2010 16:58:46 -0800 (PST) In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Jan 13, 2010 at 6:13 PM, Mike Mestnik wrote: > What should this value be? =A0From what I gather it should be the len= gth > of data stored on a single disk for each RAID level block. =A0If that= 's > the case how is it that two given data blocks are calculated to be on > separate drives? =A0It seams to me that the stripe-width is also > essential in this regard, but the man page does not reflect this. > > For example let's say that stride=3D1, then which of the following > blocks are not on the same drive as 1: 8 9 10? > The answer is dependent on the number data disks, like so. > Where x =3D n - 1 or n depending on the RAID type. > if x =3D 2 then 9 > if x =3D 3 then 8 and 10 > if x =3D 5 then 8 and 9 > Wait!! I got this all wrong, one would need all of x, n, and stride to successfully determine the disk used for a given stride. Seams to me mkfs is missing some parameters. What about [-g blocks-per-group]... http://tldp.org/HOWTO/Software-RAID-0.4x-HOWTO-8.html > There is no way to make this calculation with out knowing x, further > more calculating x based of of both stride and stripe-width is round > about... =A0Why not simply ask for x, the number of data disks and ha= ve > stripe-width be the value that is calculated, as stride might not go > into stripe-width evenly leaving you with a headache. > > Did I locate a bug? > > Is there a better forum for this discussion? > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html