From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Small Subject: Re: 3-way mirrors Date: Tue, 28 Sep 2010 17:42:28 +0100 Message-ID: <4CA21AF4.8060308@seoss.co.uk> References: <20100907141904.3696.qmail@science.horizon.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100907141904.3696.qmail@science.horizon.com> Sender: linux-raid-owner@vger.kernel.org To: George Spelvin Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 07/09/10 15:19, George Spelvin wrote: > After some frustration with RAID-5 finding mismatches and not being > able to figure out which drive has the problem, I'm setting up a rather > intricate 5-way mirrored (x 2-way striped) system. > I know that this doesn't solve your current problem, but I wondered if the fact that mismatch_cnt is not a reliable indication of corruption on RAID1 and RAID10 is a problem with your proposed solution? I don't know how difficult it would be to fix that whilst you are at it (add a data copy in the write path). Whilst I think about it, perhaps mismatch_cnt should be dropped from RAID1 / RAID10 entirely, as it doesn't seem to be particularly useful as-is.... Perhaps the data-copy mode could be a runtime option, and mismatch_cnt would only appear when it was switched on (and a repair forced when making the transition from no-copy mode to copy mode?). Cheers, Tim. -- South East Open Source Solutions Limited Registered in England and Wales with company number 06134732. Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309