From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mikael Abrahamsson Subject: Re: raid 5 crashed Date: Thu, 2 Jun 2016 07:52:11 +0200 (CEST) Message-ID: 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> <2f3e2fe6-1810-e7bd-7dc0-483ed4f0d46b@fnarfbargle.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <2f3e2fe6-1810-e7bd-7dc0-483ed4f0d46b@fnarfbargle.com> Sender: linux-raid-owner@vger.kernel.org To: Brad Campbell Cc: linux-raid List-Id: linux-raid.ids On Thu, 2 Jun 2016, Brad Campbell wrote: > People keep saying that. I've never encountered it. I suspect it's just not Well, I have had drives that would occasionally throw a read error, but MD requires that read error to happen three times before re-writing the sector, and that never happened. See earlier discussions I had with Neil on the topic. But you're correct, I don't see this on normally functioning drives. Swapped out that drive (it didn't have any specific SMART errors either) and everything was fine. I don't know what was wrong with it, might have been something flying around in there causing spurious problems. > 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. I've seen enough read errors that I nowadays only run RAID6, never RAID5. I'd also venture to say that considering the amount of people who come on the list and who come on the #linux-raid IRC channel with "raid5, one-drive-failed, and now I have read error on another drive so my array doesn't resync, what should I do?", I'd say this is a real problem. It's not however like "if you have a good drive, reading it 5 times will yield a read error". The vendor bit error rate specification doesn't work like that, so totally agree with you there. -- Mikael Abrahamsson email: swmike@swm.pp.se