From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wols Lists Subject: Re: raid 5 crashed Date: Wed, 1 Jun 2016 16:42:16 +0100 Message-ID: <574F0258.5000108@youngman.org.uk> References: <20160511131524.GA11811@cthulhu.home.robinhill.me.uk> <574C8EB9.3070706@youngman.org.uk> <574D958F.8060209@turmel.org> <574DDCBD.40801@youngman.org.uk> <95079572-f319-ca57-a3e9-e8d00ef40248@fnarfbargle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <95079572-f319-ca57-a3e9-e8d00ef40248@fnarfbargle.com> Sender: linux-raid-owner@vger.kernel.org To: Brad Campbell , Phil Turmel , bobzer Cc: linux-raid , Mikael Abrahamsson List-Id: linux-raid.ids On 01/06/16 02:48, Brad Campbell wrote: > Now, having said that : > > Much better to try and get the array running in a read-only state with > all disks in place and clone the data from the array rather than the > disks after they've been ddrescued. In the case of a running array, a > read error on one of the array members will see the RAID attempt to get > the data from elsewhere (a reconstruction), whereas a read from a disc > cloned with ddrescue will happily just report what was a faulty sector > as a big pile of zeros, and *poof* your data is gone. > > Set the timeouts appropriately (and conservatively) to give the disks > time to actually report they can't read the sector. This will allow md > to try and get it elsewhere rather than kicking the disc out because the > storage stack timed it out as faulty. Okay - so would this be better (a lot slower, possibly, but safe ...) Use dd - so it DOES bomb on error! - and only replace the drive once you've got a clean read off it. With 2TB drives, that should work so long as they're not faulty. And if it's - JUST - a timeout issue, this'll work fine? Cheers, Wol