From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert L Mathews Subject: Re: Reassembling RAID1 after good drive was offline [newbie] Date: Mon, 05 Jan 2015 09:25:55 -0800 Message-ID: <54AAC923.1070501@tigertech.com> References: <20150104210701.GG4713@deb76.aryehleib.com> <54A9B472.9090905@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54A9B472.9090905@youngman.org.uk> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 1/4/15 1:45 PM, Wols Lists wrote: > It's only the other raids that have any error correction ability, > because they use parity etc to be able to tell which set of data is correct. In theory, yes, but in practice, they don't -- or do they? I thought that even if you use RAID 6, md doesn't check all members on each read request, calculate parities, and mask silent platter-level corruption by ignoring a member spewing bad bits. It just uses parities to fill in missing data if a member fails. Or does it actually do error detection, and I'm confused? -- Robert L Mathews, Tiger Technologies, http://www.tigertech.net/