From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f176.google.com ([74.125.82.176]:64923 "EHLO mail-we0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756676AbaFYW00 (ORCPT ); Wed, 25 Jun 2014 18:26:26 -0400 Received: by mail-we0-f176.google.com with SMTP id u56so2819574wes.7 for ; Wed, 25 Jun 2014 15:26:25 -0700 (PDT) Message-ID: <53AB4C89.1060203@gmail.com> Date: Thu, 26 Jun 2014 01:26:17 +0300 From: Konstantinos Skarlatos MIME-Version: 1.0 To: Christoph Anton Mitterer , Hugo Mills CC: linux-btrfs@vger.kernel.org Subject: Re: btrfs data dup on single device? References: <20140625074713.GE31096@carfax.org.uk> <1403707306.4857.13.camel@heisenberg.scientia.net> In-Reply-To: <1403707306.4857.13.camel@heisenberg.scientia.net> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 25/6/2014 5:41 μμ, Christoph Anton Mitterer wrote: > On Wed, 2014-06-25 at 08:47 +0100, Hugo Mills wrote: >> This has variously been possible and not over the last few years. I >> think it's finally come down on the side of "not", > I think that would really be a loss... :( > > >> The question is, why? > Well imagine you have some computer which can only have one disk drive > (laptop, etc.) and you still want at least some kind of redundancy > against bit rot errors. > > > IMO, btrfs should support most flavours out there... > - n-way duplicates on the same device (and not just DUP with n=2) For the same device there is also erasure coding, where you lose lets say 10% capacity, and have the benefit of recovering from the most probable disk errors that dont take the whole disk with them, bad sectors. > - n-way mirrors on multiple devices (i.e. what we have right now with > RAID1 plus up to classic RAID1 with copies on each device > - RAID5/6 > - n-way striped+parity with n>2 > - "stacked" layouts (RAID 10 as e.g. MD has it,... RAID50, 60) > > > And terminology should really be re-worked... IMHO it's very bad to use > the term RAID1, if it's not what classic RAID1 does. > > > Cheers, > Chris. > -- Konstantinos Skarlatos