From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: BTRFS partition usage... Date: Tue, 12 Feb 2008 08:49:34 -0500 Message-ID: <200802120849.34477.chris.mason@oracle.com> References: <200802061200.14690.chris.mason@oracle.com> <20080211.232139.14959431.davem@davemloft.net> <20080212.001104.172517283.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, btrfs-devel@oss.oracle.com To: David Miller Return-path: Received: from agminet01.oracle.com ([141.146.126.228]:10409 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757800AbYBLNuX (ORCPT ); Tue, 12 Feb 2008 08:50:23 -0500 In-Reply-To: <20080212.001104.172517283.davem@davemloft.net> Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tuesday 12 February 2008, David Miller wrote: > From: David Miller > Date: Mon, 11 Feb 2008 23:21:39 -0800 (PST) > > > 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 :-/ > > Actually it seems this is only a problem with mkfs.btrfs, it clears > out the first 64 4K chunks of the disk for whatever reason. It is a good idea to remove supers from other filesystems. I also need to add zeroing at the end of the device as well. Looks like I misread the e2fs zeroing code. It zeros the whole external log device, and I assumed it also zero'd out the start of the main FS. So, if Btrfs starts zeroing at 1k, will that be acceptable for you? -chris