From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Rowe Subject: Re: Two-disk RAID5? Date: Fri, 05 May 2006 10:31:56 +0100 Message-ID: <1146821517.4365.40.camel@kenny> References: <216D6FA68B0F304DA93E95C5B786F2D12FCBBC@bart.corp.egenera.com> <20060501171128.GA18811@harddisk-recovery.com> <445AA801.6050404@tmr.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <445AA801.6050404@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids > Sorry, I couldn't find a diplomatic way to say you're completely wrong. We don't necessarily expect a diplomatic way, but a clear and intelligent one would be helpful. In two-disk RAID5 which is it? 1) The 'parity bit' is the same as the datum. 2) The parity bit is the complement of the datum. 3) It doesn't work at a bit-wise level. Many of us feel that RAID5 looks like: parity = data[0]; for (i=1; i < ndisks; ++i) parity ^= data[i]; which implies (1). It could easily be (2) but merely saying "it's not data, it's parity" doesn't clarify matters a great deal. But I'm pleased my question has stirred up such controversy! John