From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Dobrotescu Subject: Re: Question: errors=continue behaviour for failed external journal device Date: Sat, 26 Jul 2014 20:34:45 -0400 Message-ID: <53D44925.4000903@dobrotescu.ca> References: <20140727000733.GV6725@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org To: Theodore Ts'o Return-path: Received: from mail-ie0-f175.google.com ([209.85.223.175]:49237 "EHLO mail-ie0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbaG0Aet (ORCPT ); Sat, 26 Jul 2014 20:34:49 -0400 Received: by mail-ie0-f175.google.com with SMTP id x19so5210593ier.20 for ; Sat, 26 Jul 2014 17:34:48 -0700 (PDT) In-Reply-To: <20140727000733.GV6725@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 26/07/2014 20:07, Theodore Ts'o wrote: > On Sat, Jul 26, 2014 at 11:07:59PM +0000, Vlad Dobrotescu wrote: >> If this isn't the proper place for this question, please point me in >> the right direction. >> >> I couldn't find any description on Ext4's behaviour when mounted >> with errors=continue and external journal if the journal block device >> is unavailable at mount time (or becomes unavailable at some point). >> >> I would be using CentOS 7 (kernel 3.10.0-123.4.4.el7 x86_64) and >> (probably) full data journaling on a SSD. Can someone help? > So there are two different questions. > > If you use errors=continue, there is the chance that the file system > inconsistencies that discovered could cause further file system > damage, which might lead to the loss or corruption of data files > written earlier. So it's not really recommended for most purposes, > unless you have some scheme where you are monitoring dmesgs and having > some strategy to deal with detected file system errors, or when the > system absolutely, positively must continue running, and this is more > important than potential data loss. > > If the journal block device is not present then the file system can't > be mounted, and if the system was uncleanly shut down you won't be > able to recover from the unclean shutdown by replaying the journal. > > If the journal block device is *gone*, it is possible to remove the > external journal block device, and then force a file system repair, > but if this happens after an unclean shutdown, you may very well lose > data. > > Cheers, > > - Ted Sorry if this is a duplicate, but the "Followup" didn't seem to work for me Thanks for the quick and detailed answer. If I understand it correctly, the errors= option has nothing to do with journaling, but only with FS consistency issues (which can be caused by a vanished journal, but also by other events), while the mounting itself fails in the absence of the device specified for external journaling, with no fall-back alternative. Right? Vlad