From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FC59C4338F for ; Fri, 23 Jul 2021 19:24:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58D4D60EB2 for ; Fri, 23 Jul 2021 19:24:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230125AbhGWSn5 (ORCPT ); Fri, 23 Jul 2021 14:43:57 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:47850 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229528AbhGWSn4 (ORCPT ); Fri, 23 Jul 2021 14:43:56 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id F38E6220BC; Fri, 23 Jul 2021 19:24:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1627068269; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2T8g9e/awfX3Vu+0w8TJP8RAgy26B8aoKGtGPJTE/Xs=; b=uv5xRSj1xiEVBhZllXrODnwAs6hLZAMkyG+YDDtGKfHeIZD1buAQ58swuTRm69a83WoPfy RVUpAqD2jJoCRmdBavTCMCggCbOlrT/HulVK35I81knfBbKSITed7RNPJsqjTkdQ0L+ejv GNbZH5TL/duyUq7bRkQuqg+xZz81XHY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1627068269; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2T8g9e/awfX3Vu+0w8TJP8RAgy26B8aoKGtGPJTE/Xs=; b=yBh89vvMxhyxl4DeziC1RYTgElIM7Mtqxk8tMfVztOqxIoVdDJ5zbO+nXu6wO6aSw//0Em 9nMOYki3/TfxC3Aw== Received: from ds.suse.cz (ds.suse.cz [10.100.12.205]) by relay2.suse.de (Postfix) with ESMTP id E9790A3B85; Fri, 23 Jul 2021 19:24:28 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 4DDA9DA8EB; Fri, 23 Jul 2021 21:21:45 +0200 (CEST) Date: Fri, 23 Jul 2021 21:21:45 +0200 From: David Sterba To: Roman Mamedov Cc: Qu Wenruo , David Sterba , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: allow degenerate raid0/raid10 Message-ID: <20210723192145.GF19710@suse.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Roman Mamedov , Qu Wenruo , David Sterba , linux-btrfs@vger.kernel.org References: <20210722192955.18709-1-dsterba@suse.com> <20210723140843.GE19710@twin.jikos.cz> <20210723222730.1d23f9b4@natsu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210723222730.1d23f9b4@natsu> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Jul 23, 2021 at 10:27:30PM +0500, Roman Mamedov wrote: > On Fri, 23 Jul 2021 16:08:43 +0200 > David Sterba wrote: > > > > Can we slightly enhance the output? > > > RAID0/1 really looks like a new profile now, even the "1" really means > > > the number of device. > > > > Do you have a concrete suggestion? This format was inspired by a > > discussion and suggested by users so I guess this is what people expect > > and I find it clear. It's also documented in manual page so if you think > > it's not clear or missing some important information, please let me > > know. > > It really reads like another RAID level, easily confused with RAID10. > > Or that it would flip between RAID0 and RAID1 depending on something. I think it could be confusing when the number of stripes is also another raid level, like /1 in this case. From the commit https://github.com/kdave/btrfs-progs/commit/4693e8226140289dcf8f0932af05895a38152817 /dev/vdc, ID: 1 Device size: 1.00GiB Device slack: 0.00B Data,RAID0/2: 912.62MiB Data,RAID0/3: 912.62MiB Metadata,RAID1: 102.38MiB System,RAID1: 8.00MiB Unallocated: 1.00MiB it's IMHO clear or at least prompting to read the docs what it means. > Maybe something like RAID0d1? That looks similar to RAID1c3 which I'd interpret as a new profile as well. The raid56 profiles also print the stripe count so I don't know if eg. RAID5d4 is really an improvement. A 4 device mix of raid56 data and metadata would look like: # btrfs dev us . /dev/sda10, ID: 1 Device size: 10.00GiB Device slack: 0.00B Data,RAID5/4: 1.00GiB Metadata,RAID6/4: 64.00MiB System,RAID6/4: 8.00MiB Unallocated: 8.93GiB /dev/sda11, ID: 2 Device size: 10.00GiB Device slack: 0.00B Data,RAID5/4: 1.00GiB Metadata,RAID6/4: 64.00MiB System,RAID6/4: 8.00MiB Unallocated: 8.93GiB /dev/sda12, ID: 3 Device size: 10.00GiB Device slack: 0.00B Data,RAID5/4: 1.00GiB Metadata,RAID6/4: 64.00MiB System,RAID6/4: 8.00MiB Unallocated: 8.93GiB /dev/sda13, ID: 4 Device size: 10.00GiB Device slack: 0.00B Data,RAID5/4: 1.00GiB Metadata,RAID6/4: 64.00MiB System,RAID6/4: 8.00MiB Unallocated: 8.93GiB Maybe it's still too new so nobody is used to it and we've always had problems with the raid naming scheme anyway.