From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruce Merry Subject: Re: What to do about Offline_Uncorrectable and Pending_Sector in RAID1 Date: Mon, 14 Nov 2016 17:52:35 +0200 Message-ID: References: <942ab8be-cd5c-c6d1-d077-cd295b355c0c@youngman.org.uk> <5828D5DA.1070406@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <5828D5DA.1070406@youngman.org.uk> Sender: linux-raid-owner@vger.kernel.org To: Wols Lists Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 13 November 2016 at 23:06, Wols Lists wrote: > Sounds like that drive could need replacing. I'd get a new drive and do > that as soon as possible - use the --replace option of mdadm - don't > fail the old drive and add the new. Would you mind explaining why I should use --replace instead of taking out the suspect drive? I guess I lose redundancy for any writes that occur while the rebuild is happening, but I'd plan to do this with the filesystem unmounted so there wouldn't be any writes. What I'd quite like to do is treat the "good" drive as the source for all the data (unless it turns out to have bad sectors too...), even if the other drive doesn't have a read error; which I'd achieve by failing the "bad" drive. I want to do this because after doing one scrub and starting on a second, I'm still seeing non-zero mismatch_cnt. Does --replace do anything clever about using the old drive only when it must, or does it just read from the whole array like normal, which might mean taking the mismatched data from the bad drive? Thanks Bruce -- Dr Bruce Merry bmerry <@> gmail <.> com http://www.brucemerry.org.za/ http://blog.brucemerry.org.za/