From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= Subject: Re: Bit-Rot Date: Mon, 6 Mar 2017 13:56:48 +0200 Message-ID: <20170306115648.GG7497@reaktio.net> References: <95588e39-f42e-54d4-e7ff-a70af51a77c1@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: Gandalf Corvotempesta , Anthony Youngman , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sun, Mar 05, 2017 at 09:15:39AM +0100, Mikael Abrahamsson wrote: > On Fri, 3 Mar 2017, Gandalf Corvotempesta wrote: > > >This is what ZFS does. This is what Gluster does. This is what BRTFS does. > >Adding this in mdadm could be an interesting feature. > > This has been discussed several times. Yes, it would be interesting. > It's not easy to do because mdadm maps 4k blocks to 4k blocks. Only > way to "easily" add this I imagine, would be to have an additional > "checksum" block, so that raid6 would require 3 extra drives instead > of 2. > > The answer historically has been "patches welcome". > There was/is an early prototype implementation of checksums for Linux MD RAID: http://pages.cs.wisc.edu/~bpkroth/cs736/md-checksums/ http://pages.cs.wisc.edu/~bpkroth/cs736/md-checksums/md-checksums-presentation.pdf http://pages.cs.wisc.edu/~bpkroth/cs736/md-checksums/md-checksums-paper.pdf http://pages.cs.wisc.edu/~bpkroth/cs736/md-checksums/md-checksums-code.tar.bz2 Also there's the T10 DIF / DIX (Data Integrity Fields / Data Integrity eXtensions) functionality that could be used, at least if the hardware setup is SAS-based (SAS HBA + enterprise SAS disks and modern enough firmware on both that enable DIF/DIX..). I guess MD RAID could also 'emulate' T10 DIF/DIX even if the HBA/disks don't support it.. but dunno if that makes any sense. > -- > Mikael Abrahamsson email: swmike@swm.pp.se -- Pasi