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=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 80F04C433E0 for ; Wed, 27 May 2020 18:48:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BFE12089D for ; Wed, 27 May 2020 18:48:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=colorremedies-com.20150623.gappssmtp.com header.i=@colorremedies-com.20150623.gappssmtp.com header.b="O5BNeYRD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726974AbgE0Srw (ORCPT ); Wed, 27 May 2020 14:47:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56646 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726770AbgE0Srg (ORCPT ); Wed, 27 May 2020 14:47:36 -0400 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 583CDC008634 for ; Wed, 27 May 2020 11:41:12 -0700 (PDT) Received: by mail-wr1-x444.google.com with SMTP id q11so13001705wrp.3 for ; Wed, 27 May 2020 11:41:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=colorremedies-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=PWNMZFYDlyQB4xa2P67RaXs3SsINgtYYV4uVegCiE50=; b=O5BNeYRDou/1Ddic0mE/rtmpYGt9KXsU111IPk+JrGiywMmKTtvO1ZYKMWSqRqyH1J NkpmYi2Y6hjV04x1KBfZVW8lFdcf00D3pxKuIr4Mf324hpNl+0IGVkg+Y1zV0xPVtddU HbGUbm6/0yzl6XgPs77NdRPeXxb6HtWcvY2boceEOvwDWIrifIIj7p2KwENgF/nV1bXi peSzFJPnNb7gthQMSij4smJErwdD8UPT9CDjRlkJDyoMRMSzlcMw7idF7AxeEgQEgLBc 0MNSn/K4Re6nnWAAzODhjPaNzlCBEs/ZKIivUArogl+PbgNHioUmcsu9p9FnS6ZjB/xr OjJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=PWNMZFYDlyQB4xa2P67RaXs3SsINgtYYV4uVegCiE50=; b=NeN24ihqJpsON4BVghyudyR5Htv3ElcdxKfziQ2kdadJA0h+ad84hdBre1v9iHaRt9 ai64G6lDb2GUnXEibkW/br5NGoE3ov2v3idFarTrveRVqrjytXvlUrCmDzTmpxcwLR5+ E3Iq7Q82FcitVkDQLHAcxjqfil2ix8U2yJQKUH/0vt+VPam4+RUmDrAFdNHFxgupoN0Q bSTVSBPNyXeco9pJ756XkfU2PdU5fnl1WYh5AAhQM46WPi7rcjTq3CHgNJK7a02DjhrC i36Kp7pTmcXNPFc0d4Z/+F9h4vp6CZXbux/XzThUgC3UvY4CjxA3T9+XqdU02Djsc8Cd RxBw== X-Gm-Message-State: AOAM533BGouRuGQJXkW8i/Vx+8l11Xgm0W7MhLSMVKBfv0prc7cRdTdN 2MrtRTQAAVYVkBYZBKWlw/XugS1BHp3W7Jzs+gSMqw== X-Google-Smtp-Source: ABdhPJx5h6fA9dSeSHd5qX+wLv/eEgrw6zjx2jHRdX1nGjNWWnYXzuTt+UQLlN3DlXnhbD5u2kc/O6FRbxPmmgH4FBg= X-Received: by 2002:a5d:4d4d:: with SMTP id a13mr17118329wru.252.1590604871090; Wed, 27 May 2020 11:41:11 -0700 (PDT) MIME-Version: 1.0 References: <46fa65a3-137b-3164-0998-12bb996c15ef@gmail.com> <0d3b740d-a431-cca0-3841-a85e49ffff9e@libero.it> In-Reply-To: <0d3b740d-a431-cca0-3841-a85e49ffff9e@libero.it> From: Chris Murphy Date: Wed, 27 May 2020 12:40:55 -0600 Message-ID: Subject: Re: Planning out new fs. Am I missing anything? To: Goffredo Baroncelli Cc: Chris Murphy , Andrei Borzenkov , Justin Engwer , Btrfs BTRFS Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, May 27, 2020 at 10:23 AM Goffredo Baroncelli w= rote: > > Hi All, > > On 5/27/20 8:25 AM, Chris Murphy wrote: > > On Tue, May 26, 2020 at 11:22 PM Andrei Borzenkov = wrote: > >> > >> 27.05.2020 05:20, Chris Murphy =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >>> > >>> single, dup, raid0, raid1 (all), raid10 are safe and stable. > >> > >> Until btrfs can reliably detect and automatically handle outdated devi= ce > >> I would not call any multi-device profiles "safe", at least unconditio= nally. > > > > I agree. > > > > Checking the generation of each device should be sufficient to detect "ou= tdated" devices. Why this check is not performed ? > May be that I am missing something ? But transid isn't unique enough except in isolation. Degraded volumes are treated completely independently. So if I take a 2x raid1 and mount each one degraded on separate computers and modify them. Then join them back together, how can Btrfs resolve the differences? It's a mess. Yes that is obviously a kind of sabotage. While not literal sabotage, the effect is the same if you have alternating degraded drives in successive boots. So you just cannot use degraded with either fstab or rootflags. It's bad advice to anyone who gives it and we need to be vigilant about recommending against it. Maybe the man 5 btrfs page should expressly say not to include degraded in fstab, or at least warn there are consequences. --=20 Chris Murphy