From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Iversen Subject: Re: Should "mdadm --add" complain if the new device appears to have a filesystem on it? Date: Tue, 23 Jul 2013 12:18:35 +0200 Message-ID: <51EE587B.8060209@iversen-net.dk> References: <20130723113902.62368e3e@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Holger Kiehl Cc: NeilBrown , linux RAID List-Id: linux-raid.ids On 2013-07-23 09:41, Holger Kiehl wrote: > Hello Neil, > > first, many many thanks for all your good work on MD and always helping > us here on this list! > > On Tue, 23 Jul 2013, NeilBrown wrote: > >> >> As you probably know, when you use "mdadm -C" to create an array, it will >> check if the devices appear to contain a filesystem or similar already >> and >> will complain if they do - requiring you do say "yes" or use "--run" >> to avoid >> the warning. >> >> However if you use "--add" to add a device to an existing array no such >> checks are done. So it isn't too hard to destroy all those cat photos >> you >> have saved on a USB drive (because device names change every time you >> boot >> and you got confused). >> >> >> I could easily change "--add" to be more cautious, but that might break >> existing scripts, which I would rather not do. >> >> Or I could add a "policy" line to mdadm.conf which would indicate the >> policy >> for "--add" - either "spare" or "force-spare". But then I would need to >> decide on a default. The default should probably be safe otherwise >> people >> probably won't change it until they get burned. So people with >> scripts would >> still experience breakage, but could now fix it easily with a "policy" >> line. >> >> Or maybe "--add" should be deprecated so people have to choose between >> "--re-add" or a new "--spare" with --spare requiring "--force" to destroy >> data. >> Then "--add" would generate a deprecation message which scripts could >> ignore >> but people might learn from. >> >> >> I don't think there is an obviously-correct answer here so I'm open to >> suggestions. What do people think? >> > I first thought of a --initialize, but I do not think it is any better. > So I would vote for the second solution, depreciating --add and using > --spare plus --force. If we have to change the options anyway, then I'm more in the mood for --add --force for new volumes, and --add for existing ones. It would be more in line with what we have now, IMHO. (please CC, not on the list) -- Med venlig hilsen Christian Iversen