From: Andi Kleen Subject: Re: [RFC][PATCH] Multiple mount protection Date: Fri, 1 Jun 2007 14:13:39 +0200 Message-ID: <20070601121339.GF7217@one.firstfloor.org> References: <1179777153.3910.13.camel@garfield> <20070601114100.GB13905@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andi Kleen , Kalpak Shah , linux-ext4 , Andreas Dilger To: Theodore Tso Return-path: Received: from one.firstfloor.org ([213.235.205.2]:41652 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750719AbXFAMNn (ORCPT ); Fri, 1 Jun 2007 08:13:43 -0400 Content-Disposition: inline In-Reply-To: <20070601114100.GB13905@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org > Unfortunately, it's not possible to do what you suggest, since one of > the whole points of increasing the sequence number every 5 seconds is > to act as a keep-alive, so another machine trying to access the shared Clusters usually have other ways to do this, haven't they? Typically they have STONITH too. It's probably too simple minded to just replace a real cluster setup which also handles split brain and other conditions. So it's purely against mistakes. Besides relying on it would seem dangerous because it is not synchronous and you could do a lot of damage in 5 seconds. The rationale of the lazy writing would be that at least in usual operation super block should be written regularly and with 5 seconds delay just being a not fully reliable heuristic it probably doesn't matter if the possible delay is a little longer even. -Andi