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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 3FF62CA9EAF for ; Mon, 21 Oct 2019 15:27:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0FAA3206C2 for ; Mon, 21 Oct 2019 15:27:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=liland-com.20150623.gappssmtp.com header.i=@liland-com.20150623.gappssmtp.com header.b="2GFdufV7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727739AbfJUP16 (ORCPT ); Mon, 21 Oct 2019 11:27:58 -0400 Received: from mail-wm1-f49.google.com ([209.85.128.49]:53537 "EHLO mail-wm1-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726289AbfJUP16 (ORCPT ); Mon, 21 Oct 2019 11:27:58 -0400 Received: by mail-wm1-f49.google.com with SMTP id i16so13819352wmd.3 for ; Mon, 21 Oct 2019 08:27:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=liland-com.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=Brl5AWXM71hF9rdolS1WFaiWGE9ik+7jokzQG/KsuDM=; b=2GFdufV7DqvAvwWXHZ0fBdpy+jd/29qudH8kUCz1vG4seueZX7Ntnq4FrW/HW3YJVY 0CFhJdS++M+WxBvRsgUP+Z189l2aLgkKZD89lHaAgNKLQPKkoNFlyLLKVSkba217rx2M KSD6LIOodQgqdyNnZX4zXKKcDKpj9QbkazpBKcjTSF1JsOpMhHafssat2m+1AJ6hiDHZ 3sqaNsZ9X13q7x4rNu2fJtOF24UfpZcbpCq4CYWT97AUABJX2+mdaZrgZErE6zH5uxjc tj0l/y0ekCNFZLZpy1sPaWaxvyRMFGY0Pqgd096Z/XzzrMlxcPqOcPVKeyvJs56Rpyxa xBpA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=Brl5AWXM71hF9rdolS1WFaiWGE9ik+7jokzQG/KsuDM=; b=c0/IFw/TBlNgBGQQOZ82+Tj/TU2tIk5g31ngj9gV1GwJXWGwxz39nmAU3Qe4jWYFwC bkXruc7f0dO/ylA5QeGlXnLDFhoI+iz7FJ2ScBlGV2O18xwDpiYcN6XIKL3ToODxJS9O Fbm5S+tLSSGE/jLMUryCNOYohNJiLpWYDr72b6sbT1kwkE2yIlTd0DJWAK4JgudRvJeJ 4ACbYJSKzZd9G5AchlaRWeCl7Y/6tSp3d0cthlFeaeBWfc+VVBpZ51BK9GkSHYLNLdAL qkLaX244gmouEfz61Noq2yQtIGg/3D/4Q4HlL9zWFxcfBQzLpj8OoDMMzjCGvxhg/pmD mslg== X-Gm-Message-State: APjAAAWcqnLthaQy8su4Zo9sdCoJF0NUSGuMjLzYqhJDqHbJg2bWgeuK BbJ31iwV01spqnjCitBx/BgagmQMGwrZW8ye0NGkktSVJhVAIpdJ0Gl542xh8F31eAWaJfpRuBw HgUJhnUlLfy7XogzffHxM+zs/P7o= X-Google-Smtp-Source: APXvYqxEDTiF/cB1zsyOS9Te3Xt14xmljgPltE0eq8O1jnQ0JZFoW4WfjdEr7QVFJiQ2lVd8PT6uug== X-Received: by 2002:a1c:3b42:: with SMTP id i63mr18502856wma.37.1571671676418; Mon, 21 Oct 2019 08:27:56 -0700 (PDT) Received: from [192.168.0.121] ([62.218.42.35]) by smtp.gmail.com with ESMTPSA id f83sm15109030wmf.43.2019.10.21.08.27.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Oct 2019 08:27:55 -0700 (PDT) Subject: Re: MD RAID 5/6 vs BTRFS RAID 5/6 To: Zygo Blaxell Cc: linux-btrfs@vger.kernel.org References: <20191016194237.GP22121@hungrycats.org> From: Edmund Urbani Message-ID: <067d06fc-4148-b56f-e6b4-238c6b805c11@liland.com> Date: Mon, 21 Oct 2019 17:27:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20191016194237.GP22121@hungrycats.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en-GB Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 10/16/19 9:42 PM, Zygo Blaxell wrote: > > For raid5 I'd choose btrfs -draid5 -mraid1 over mdadm raid5 > sometimes--even with the write hole, I'd expect smaller average data > losses than mdadm raid5 + write hole mitigation due to the way disk > failure modes are distributed. =20 What about the write hole and RAID-1? I understand the write hole is most commonly associated with RAID-5, but it is also a problem with other RAID l= evels. You would need to scrub after a power failure to be sure that no meta data = gets corrupted even with RAID-1. Otherwise you might still have inconsistent cop= ies and the problem may only become apparent when one drive fails. Can we be ce= rtain that scrubbing is always able to fix such inconsistencies with RAID-1? Regards, =C2=A0Edmund --=20 *Liland IT GmbH* Ferlach =E2=97=8F Wien =E2=97=8F M=C3=BCnchen Tel: +43 463 220111 Tel: +49 89=20 458 15 940 office@Liland.com https://Liland.com =C2=A0 Copyright =C2=A9 2019 Liland IT GmbH=C2=A0 Diese Mail enthaelt vertrauliche und/oder=20 rechtlich geschuetzte=C2=A0Informationen.=C2=A0 Wenn Sie nicht der richtige Adressat=20 sind oder diese Email irrtuemlich=C2=A0erhalten haben, informieren Sie bitt= e=20 sofort den Absender und vernichten=C2=A0Sie diese Mail. Das unerlaubte Kopi= eren=20 sowie die unbefugte Weitergabe=C2=A0dieser Mail ist nicht gestattet.=C2=A0 This=20 email may contain confidential and/or privileged information.=C2=A0 If you are=20 not the intended recipient (or have received this email in=C2=A0error) plea= se=20 notify the sender immediately and destroy this email. Any=C2=A0unauthorised= =20 copying, disclosure or distribution of the material in this=C2=A0email is= =20 strictly forbidden.