From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from magic.merlins.org ([209.81.13.136]:50076 "EHLO mail1.merlins.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756175AbaEEV21 (ORCPT ); Mon, 5 May 2014 17:28:27 -0400 Date: Mon, 5 May 2014 14:28:16 -0700 From: Marc MERLIN To: Hugo Mills , Btrfs mailing list Subject: Re: Thoughts on RAID nomenclature Message-ID: <20140505212816.GT10159@merlins.org> References: <20140505211738.GS24298@carfax.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20140505211738.GS24298@carfax.org.uk> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Mon, May 05, 2014 at 10:17:38PM +0100, Hugo Mills wrote: > Given these four (spread, dup, linear, grouped), I think it's > fairly obvious that spread is a special case of grouped, where each > device is its own group. Then dup is the opposite of grouped (i.e. you > must have one or the other but not both). Finally, linear is a > modifier that changes the sort order. > > All of these options run completely independently of the actual > replication level selected, so we could have 3c:spread,linear > (allocates on the first three devices only, until one fills up and > then it moves to the fourth device), or 2c2s:grouped, with a device > mapping {sda:1, sdb:1, sdc:1, sdd:2, sde:2, sdf:2} which puts > different copies on different device controllers. I generally like the idea and proposal :) Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901