From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: BTRFS partition usage... Date: Mon, 11 Feb 2008 23:21:39 -0800 (PST) Message-ID: <20080211.232139.14959431.davem@davemloft.net> References: <200802061200.14690.chris.mason@oracle.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, btrfs-devel@oss.oracle.com To: chris.mason@oracle.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:42678 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1758695AbYBLHVH (ORCPT ); Tue, 12 Feb 2008 02:21:07 -0500 In-Reply-To: <200802061200.14690.chris.mason@oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Filesystems like ext2 put their superblock 1 block into the partition in order to avoid overwriting disk labels and other uglies. UFS does this too, as do several others. One of the few exceptions I've been able to find is XFS. This is a real issue on sparc where the default sun disk labels created use an initial partition where block zero aliases the disk label. It took me a few iterations before I figured out why every btrfs make would zero out my disk label :-/