From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 7 Sep 2004 14:28:40 +0200 From: Lars Marowsky-Bree To: Philipp Reisner , drbd-dev@lists.linbit.com Subject: Re: [Drbd-dev] Another drbd race Message-ID: <20040907122840.GA15272@marowsky-bree.de> References: <20040819110202.GO9601@marowsky-bree.de> <200409071139.29609.philipp.reisner@linbit.com> <20040907101343.GA5638@nudl> <200409071419.55799.philipp.reisner@linbit.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200409071419.55799.philipp.reisner@linbit.com> Cc: List-Id: Coordination of development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 2004-09-07T14:19:55, Philipp Reisner said: > N1 net N2 > P/S --- S/P everything up and running. > P/? - - S/? network breaks ; N1 freezes IO > P/? - - S/? N1 fences N2: > In the Stonith case: turn off N2. > In the "smart" case: > N1 asks N2 to fence itself from the storage via cnet. > HB calls "drbdadm fence r0" on N2. > N2 replies to N1 that fencins is done via cnet. > N1 calls "drbdadm peer-dead r0". > P/D - - S/? N1 thaws IO In this scenario, there is no need to have a special 'fence' operation. IO is already frozen, so we can simply 'stop' drbd on N2 if we so chose. (Which will freeze the generation counter, will set the Outdated flag etc.) > N2 got the the "Outdated" flag set in its meta-data, by the "fence" > command. I am not sure if it should be called "fence", other ideas: > "considered-dead","die","fence","outdate". What do you think ? > > My question is: > Is it planed that heartbeat will be able to perform this kind of fencing ? It actually comes for free. If however heartbeat fences or stops N1 in this case, we'll deliver a (successful) stop or fence notification to the incarnation running on N2, which will call out to 'drbdadm mark-peer-dead' and basically do the same. You may find http://wiki.trick.ca/linux-ha/ClusterResourceManager_2fMultipleIncarnationResources an interesting read here. (Also the link to the MultiStateResources in there.) It's almost implemented, the drbd agent is already written (proof of concept code stage), and Andrew tells me we'll have the multiple incarnations within a few weeks too. Sincerely, Lars Marowsky-Brée -- High Availability & Clustering \\\ /// SUSE Labs, Research and Development \honk/ SUSE LINUX AG - A Novell company \\//