From: Mike Mestnik Subject: How to use mkfs.ext4 "stride=" on RAID correctly? Date: Wed, 13 Jan 2010 18:12:13 -0600 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: linux-ext4@vger.kernel.org Return-path: Received: from mail-ew0-f209.google.com ([209.85.219.209]:43499 "EHLO mail-ew0-f209.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755014Ab0ANAMQ (ORCPT ); Wed, 13 Jan 2010 19:12:16 -0500 Received: by ewy1 with SMTP id 1so269197ewy.28 for ; Wed, 13 Jan 2010 16:12:14 -0800 (PST) Sender: linux-ext4-owner@vger.kernel.org List-ID: What should this value be? From what I gather it should be the length of data stored on a single disk for each RAID level block. If that's the case how is it that two given data blocks are calculated to be on separate drives? It 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=1, 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 = n - 1 or n depending on the RAID type. if x = 2 then 9 if x = 3 then 8 and 10 if x = 5 then 8 and 9 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... Why not simply ask for x, the number of data disks and have 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?