From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brad Campbell Subject: Re: raid 5 crashed Date: Thu, 2 Jun 2016 07:15:32 +0800 Message-ID: <2f3e2fe6-1810-e7bd-7dc0-483ed4f0d46b@fnarfbargle.com> 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> <20b1858b-0cd7-a7de-82af-9167dbcfb09e@fnarfbargle.com> <574F00F5.80801@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <574F00F5.80801@youngman.org.uk> Sender: linux-raid-owner@vger.kernel.org To: Wols Lists , Edward Kuns Cc: Phil Turmel , bobzer , linux-raid , Mikael Abrahamsson List-Id: linux-raid.ids On 01/06/16 23:36, Wols Lists wrote: > On 01/06/16 05:07, Brad Campbell wrote: >> I have however done a *lot* of data recovery on single drives over the >> years and can absolutely vouch that dd will leave you in tears. > Good to know! I've regularly used dd on drives, but not on ones that > were in trouble (maybe once ...) > > But now drives are at the point that you cannot guarantee an error-free > scan even on just one pass, People keep saying that. I've never encountered it. I suspect it's just not the problem that the hysterical ranting makes it out to be (either that or the pile of cheap and nasty drives I have here are model citizens). I've *never* seen a read error unless the drive was in trouble, and that includes running dd reads in a loop over multiple days continuously. If it were that bad I'd see drives failing SMART long tests routinely also, and that does not happen either. -- Dolphins are so intelligent that within a few weeks they can train Americans to stand at the edge of the pool and throw them fish.