From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mondschein.lichtvoll.de ([194.150.191.11]:47256 "EHLO mail.lichtvoll.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751253Ab3CJLX7 convert rfc822-to-8bit (ORCPT ); Sun, 10 Mar 2013 07:23:59 -0400 From: Martin Steigerwald To: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 0/5] [RFC] RAID-level terminology change Date: Sun, 10 Mar 2013 12:23:56 +0100 Cc: Hugo Mills References: <1362861071-12589-1-git-send-email-hugo@carfax.org.uk> (sfid-20130310_104347_651723_C84E4102) In-Reply-To: <1362861071-12589-1-git-send-email-hugo@carfax.org.uk> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Message-Id: <201303101223.56805.Martin@lichtvoll.de> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi Hugo, Am Samstag, 9. März 2013 schrieb Hugo Mills: > 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 What does the "D" in "2CD" mean? Its not explained above, unless I miss something. > RAID-10 2CmS > RAID-5 1CmS1P > RAID-6 1CmS2P I think its great to clarify the RAID-level terminology, but I find the new notation a bit, hmmm, cryptic. Maybe for displaying it would be nice to show a more verbose format like 2 copies, many stripes, 1 parity (1CmS1P) by default and the abbreviated one in parentheses? Any other idea to make it less cryptic? Thanks, -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7