Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422892AbWBIRGb (ORCPT ); Thu, 9 Feb 2006 12:06:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965234AbWBIRGb (ORCPT ); Thu, 9 Feb 2006 12:06:31 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:41227 "EHLO spitz.ucw.cz") by vger.kernel.org with ESMTP id S1422892AbWBIRGa (ORCPT ); Thu, 9 Feb 2006 12:06:30 -0500 Date: Wed, 8 Feb 2006 21:58:03 +0000 From: Pavel Machek To: Bill Davidsen Cc: Phillip Susi , linux-kernel@vger.kernel.org Subject: Re: FYI: RAID5 unusably unstable through 2.6.14 Message-ID: <20060208215802.GE2353@ucw.cz> References:

<43CD8A19.3010100@cfl.rr.com> <43E2834F.8040009@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43E2834F.8040009@tmr.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 964 Lines: 31 Hi! > >If 1 disk has a 1/1000 chance of failure, then > >2 disks have a (1/1000)^2 chance of double failure, and > >3 disks have a (1/1000)^2 * 3 chance of double failure > >4 disks have a (1/1000)^2 * 7 chance of double failure > > After the first drive fails you have no redundancy, the > chance of an additional failure is linear to the number > of remaining drives. > > Assume: > p - probability of a drive failing in unit time > n - number of drives > F - probability of double failure > > The chance of a single drive failure is n*p. After that Actually it is not. Imagine 100 drives with 10% failure rate each. You can't have probability of 1000%... Pavel -- Thanks, Sharp! - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/