From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piergiorgio Sartor Subject: Re: Formatting of backing device Date: Fri, 17 Feb 2012 00:17:54 +0100 Message-ID: <20120216231754.GA14206@lazy.lzy> References: <20120201214443.GA8544@lazy.lzy> <20120202190122.GA2353@lazy.lzy> <20120202221101.GA26768@google.com> <20120202222431.GA7171@lazy.lzy> <20120216203332.GA6597@lazy.lzy> <20120216223554.GA6947@lazy.lzy> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Joseph Glanville Cc: Piergiorgio Sartor , Alex Elsayed , linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org Hi joseph, > Your reasoning is quite sound assuming the cache device is present at > activation time. > > In the case where the cache device has failed but the backing device > has persisted the failure then the case looks somewhat more like this: > 1) OS probes all devices, searches for caches and finds none. > 2) Activate the raw backing device with possibly corrupt data.... as I mentioned, this is a bit borderline. One reason is that it would be a failure in any case, depending on what the system will do with the backing device. Second, as per md, the configuration could be in a file in initramfs, which will allow to support this type of failure *and* have the backing device unformatted. In other words, it does not need to be activated automatically by kernel, it can be done by the user, like md... As wrote before, I'm fine with the formatting, very clear and understandable. bye, -- piergiorgio