From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: Please revert a91a2785b20 Date: Tue, 29 Mar 2011 09:42:08 -0400 Message-ID: References: <20110328230319.GA12790@redhat.com> <4D918347.7050500@fusionio.com> <20110329132032.GA22921@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20110329132032.GA22921@redhat.com> (Mike Snitzer's message of "Tue, 29 Mar 2011 09:20:32 -0400") Sender: linux-kernel-owner@vger.kernel.org To: Mike Snitzer Cc: Jens Axboe , Thomas Gleixner , Linus Torvalds , Andrew Morton , LKML , "Martin K. Petersen" , James Bottomley , "Rafael J. Wysocki" , Ingo Molnar , dm-devel@redhat.com, neilb@suse.de List-Id: dm-devel.ids >>>>> "Mike" == Mike Snitzer writes: Mike, Mike> But I think we have a related issue that needs discussion, given Mike> that an integrity profile mismatch will cause MD's assemble to Mike> fail (rather than warn and continue to assemble without integrity Mike> support). Mike> DM doesn't fail to load a DM device due to a integrity profile Mike> mismatch; it just emits a warning and continues. Mike> In contrast, MD will now disallow adding a normal disk (without Mike> integrity support) to an array that has historically had a Mike> symmetric integrity profile across all members. You would invalidate all your existing integrity metadata, tagging, etc. on existing metadevice members. That seems to be a policy decision, so if we go down that path it would have to be keyed off a force assembly option passed down from userland tooling. Turning off features and/or losing metadata really should not be done without the user's explicit consent. Also, let's assume you run an integrity-aware app on a DM device and you add a non-integrity drive. The DM device is then no longer capable of carrying integrity metadata out to storage. What happens to the app? What about outstanding writes with metadata attached? Good discussion topic for next week, methinks... -- Martin K. Petersen Oracle Linux Engineering