From mboxrd@z Thu Jan 1 00:00:00 1970 From: Larkin Lowrey Subject: Q wrt LVM snapshot of ext4 w/ external journal Date: Tue, 13 Apr 2010 13:22:35 -0500 Message-ID: <4BC4B66B.9000205@nuclearwinter.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: linux-ext4@vger.kernel.org Return-path: Received: from titan.nuclearwinter.com ([209.40.204.131]:54012 "EHLO titan.nuclearwinter.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694Ab0DMTIf (ORCPT ); Tue, 13 Apr 2010 15:08:35 -0400 Received: from [10.0.0.100] (c-98-196-242-36.hsd1.tx.comcast.net [98.196.242.36]) (authenticated bits=0) by titan.nuclearwinter.com (8.14.1/8.14.1) with ESMTP id o3DILZon030712 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Tue, 13 Apr 2010 13:21:36 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: Is it safe to mount an LVM2 snapshot of an ext4 fs that has an external journal? My googling has revealed only that the snapshot procedure will cause the fs to checkpoint the journal (if that's the right term) but also that the fs will want to replay the journal when mounted, even if -o ro. If my journal is on an external device (NVRAM device in my case) I don't want the snapshot instance to interfere with the main on-line fs's use of the journal. Is there any documentation, other than code, that describes this scenario? If there is another, more appropriate, venue for my question please let me know. Thank you, --Larkin