From: Jamie Lokier Subject: Re: [PATCH 0/4] (RESEND) ext3[34] barrier changes Date: Wed, 21 May 2008 20:42:18 +0100 Message-ID: <20080521194218.GB26780@shareable.org> References: <482DDA56.6000301@redhat.com> <20080518211140.b29bee30.akpm@linux-foundation.org> <200805191316.27551.chris.mason@oracle.com> <200805191439.36577.chris.mason@oracle.com> <20080521112224.GD5028@ucw.cz> <20080521110324.668048e0.akpm@linux-foundation.org> <20080521182949.GL8581@mit.edu> <20080521114917.60bf42c7.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Tso , Pavel Machek , Chris Mason , Eric Sandeen , Andi Kleen , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Andrew Morton Return-path: Received: from mail2.shareable.org ([80.68.89.115]:59568 "EHLO mail2.shareable.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758208AbYEUTm5 (ORCPT ); Wed, 21 May 2008 15:42:57 -0400 Content-Disposition: inline In-Reply-To: <20080521114917.60bf42c7.akpm@linux-foundation.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Andrew Morton wrote: > > And as long as your 100% confident that UPS's will never fail, > > janitors will never accidentally hit the Emergency Power Office > > switch, and so on. > > Well. The product of two very small numbers is... Another unquantified very small number. You have a UPS, but the first time you discover it's not wired up properly is when it fails. This happened recently in a customer's office... The UPS power wiring melted, leaving a big stinking hole, and all the servers went down - quickly. Another is misconfiguring the UPS daemon so it continues writing to disk for 30 minutes until the battery runs down... Like the chance of two disks going wrong in a RAID at the same time... that would *never* happen would it? *tip-toes out of the room* -- Jamie