From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:39760 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753249Ab3CJXzZ (ORCPT ); Sun, 10 Mar 2013 19:55:25 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1UEq5g-000420-EV for linux-btrfs@vger.kernel.org; Mon, 11 Mar 2013 00:55:44 +0100 Received: from cpc2-with5-2-0-cust470.1-4.cable.virginmedia.com ([81.97.59.215]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 11 Mar 2013 00:55:44 +0100 Received: from samtygier by cpc2-with5-2-0-cust470.1-4.cable.virginmedia.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 11 Mar 2013 00:55:44 +0100 To: linux-btrfs@vger.kernel.org From: sam tygier Subject: Re: [PATCH 0/5] [RFC] RAID-level terminology change Date: Sun, 10 Mar 2013 23:55:10 +0000 Message-ID: References: <1362861071-12589-1-git-send-email-hugo@carfax.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 In-Reply-To: <1362861071-12589-1-git-send-email-hugo@carfax.org.uk> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/03/13 20:31, Hugo Mills wrote: > Some time ago, and occasionally since, we've discussed altering the > "RAID-n" terminology to change it to an "nCmSpP" format, where n is the > number of copies, m is the number of (data) devices in a stripe per copy, > and p is the number of parity devices in a stripe. > > The current kernel implementation uses as many devices as it can in the > striped modes (RAID-0, -10, -5, -6), and in this implementation, that is > written as "mS" (with a literal "m"). The mS and pP sections are omitted > if the value is 1S or 0P. > > The magic look-up table for old-style / new-style is: > > single 1C (or omitted, in btrfs fi df output) > RAID-0 1CmS > RAID-1 2C > DUP 2CD > RAID-10 2CmS > RAID-5 1CmS1P > RAID-6 1CmS2P Are these the only valid options? Are 'sensible' new levels (eg 3C, mirrored to 3 disk or 1CmS3P, like raid6 with but with 3 parity blocks) allowed? Are any arbitrary levels allowed (some other comments in the thread suggest no)? Will there be a recommended (or supported) set?