From: Andreas Dilger Subject: [RFC] store RAID stride in superblock Date: Fri, 11 May 2007 19:02:48 -0700 Message-ID: <20070512020248.GQ6375@schatzie.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: linux-ext4@vger.kernel.org Return-path: Received: from mail.clusterfs.com ([206.168.112.78]:34357 "EHLO mail.clusterfs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754785AbXELCCu (ORCPT ); Fri, 11 May 2007 22:02:50 -0400 Received: from localhost.adilger.int (unknown [64.166.152.82]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.clusterfs.com (Postfix) with ESMTP id D54AD7BA307 for ; Fri, 11 May 2007 20:02:49 -0600 (MDT) Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org It is possible to specify the RAID stride to mke2fs allow it to optimize the layout of the bitmaps. With the new mballoc it is also possible to tell it via a mount option to do large allocations aligned on the RAID stride (by default it aligns on 1MB boundaries from the start of the LUN). What would be rather convenient is to store the RAID stride value in the superblock. That would spare a lot of hassle on the part of the admin to tune the filesystem optimally for the underlying storage. There is also a library used in the XFS tools that knows how to probe various kinds of block devices (e.g. MD RAID, LVM/DM, etc) to get their storage layout that would avoid the need for the user to specify anything. Any thoughts on this? Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.