From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fw11a-maira.wadns.net ([196.220.39.139]:64114 "EHLO fw11a.wadns.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751258AbaEDH1Z (ORCPT ); Sun, 4 May 2014 03:27:25 -0400 Message-ID: <5365EBCE.1060605@swiftspirit.co.za> Date: Sun, 04 May 2014 09:27:10 +0200 From: Brendan Hide MIME-Version: 1.0 To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org, Hugo Mills , Russell Coker Subject: Re: copies= option References: <201405041216.54348.russell@coker.com.au> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2014/05/04 05:27 AM, Duncan wrote: > Russell Coker posted on Sun, 04 May 2014 12:16:54 +1000 as excerpted: > >> Are there any plans for a feature like the ZFS copies= option? >> >> I'd like to be able to set copies= separately for data and metadata. In >> most cases RAID-1 provides adequate data protection but I'd like to have >> RAID-1 and copies=2 for metadata so that if one disk dies and another >> has some bad sectors during recovery I'm unlikely to lose metadata. > Hugo's the guy with the better info on this one, but until he answers... > > The zfs license issues mean it's not an option for me and I'm thus not > familiar with its options in any detail, but if I understand the question > correctly, yes. > > And of course since btrfs treats data and metadata separately, it's > extremely unlikely that any sort of copies= option wouldn't be separately > configurable for each. > > There was a discussion of a very nice multi-way-configuration schema that > I deliberately stayed out of as both a bit above my head and far enough > in the future that I didn't want to get my hopes up too high about it > yet. I already want N-way-mirroring so bad I can taste it, and this was > that and way more... if/when it ever actually gets coded and committed to > the mainline kernel btrfs. As I said, Hugo should have more on it, as he > was active in that discussion as it seemed to line up perfectly with his > area of interest. > The simple answer is yes, this is planned. As Duncan implied, however, it is not on the immediate roadmap. Internally we appear to be referring to this feature as "N-way redundancy" or "N-way mirroring". My understanding is that the biggest hurdle before the primary devs will look into N-way redundancy is to finish the Raid5/6 implementation to include self-healing/scrubbing support - a critical issue before it can be adopted further. -- __________ Brendan Hide http://swiftspirit.co.za/ http://www.webafrica.co.za/?AFF1E97