Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030225AbWARLYf (ORCPT ); Wed, 18 Jan 2006 06:24:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030226AbWARLYf (ORCPT ); Wed, 18 Jan 2006 06:24:35 -0500 Received: from dtp.xs4all.nl ([80.126.206.180]:16346 "HELO abra2.bitwizard.nl") by vger.kernel.org with SMTP id S1030225AbWARLYf (ORCPT ); Wed, 18 Jan 2006 06:24:35 -0500 Date: Wed, 18 Jan 2006 12:24:31 +0100 From: Erik Mouw To: Kyle Moffett Cc: Michael Loftis , linux-kernel@vger.kernel.org Subject: Re: FYI: RAID5 unusably unstable through 2.6.14 Message-ID: <20060118112431.GA11868@harddisk-recovery.nl> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Harddisk-recovery.com User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1259 Lines: 26 On Tue, Jan 17, 2006 at 07:12:57PM -0500, Kyle Moffett wrote: > The most reliable RAID-5 you can build is a 3-drive system. For each > byte of data, you have a half-byte of parity, meaning that half the > data-space (not including the parity) can fail without data loss. > I'm ignoring the issue of rotating parity drive for simplicity, but > that only affects performance, not the algorithm. If you want any > kind of _real_ reliability and speed, you should buy a couple good > hardware RAID-5 units and mirror them in software. Actually, the most reliable RAID-5 is a 2 drive system, where you have a full byte of reduncancy for each byte of data. Two drive RAID-5 systems are usually called RAID-1, but if you write out the formulas it becomes clear that RAID-1 is just a special case of RAID-5. Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands | Data lost? Stay calm and contact Harddisk-recovery.com - 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/