From: Andreas Dilger Subject: Re: changing stride and stripe_width post-fs-creation? Date: Tue, 20 Oct 2009 15:08:51 -0600 Message-ID: References: <7284e2210910201032h74cf437bm6043d97748ece4c9@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; CHARSET=US-ASCII; delsp=yes; format=flowed Content-Transfer-Encoding: 7BIT Cc: linux-ext4@vger.kernel.org To: Doug Hunley Return-path: Received: from sca-es-mail-2.Sun.COM ([192.18.43.133]:42738 "EHLO sca-es-mail-2.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750990AbZJTVIv (ORCPT ); Tue, 20 Oct 2009 17:08:51 -0400 Received: from fe-sfbay-10.sun.com ([192.18.43.129]) by sca-es-mail-2.sun.com (8.13.7+Sun/8.12.9) with ESMTP id n9KL8ubM006861 for ; Tue, 20 Oct 2009 14:08:56 -0700 (PDT) Received: from conversion-daemon.fe-sfbay-10.sun.com by fe-sfbay-10.sun.com (Sun Java(tm) System Messaging Server 7u2-7.04 64bit (built Jul 2 2009)) id <0KRT00K00ZUOR900@fe-sfbay-10.sun.com> for linux-ext4@vger.kernel.org; Tue, 20 Oct 2009 14:08:56 -0700 (PDT) In-reply-to: <7284e2210910201032h74cf437bm6043d97748ece4c9@mail.gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 20-Oct-09, at 11:32, Doug Hunley wrote: > Is it safe to use tune2fs to alter stride and stripe_width on an ext4 > fs once it has been created? Any caveats I should know about? Thanks The stride is mostly used at fs creation time, but there is no problem with changing it. The stripe_width is used by the allocator to align file allocations with the RAID layout. One question for Eric is whether the new libdisk patches he made will set the stripe_width to something ridiculous like 512 or 4096 bytes, or if it just leaves that field unset in that case. I suspect it would be bad for mballoc to see the stripe_width be such a small value. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.