From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mxex1.tik.uni-stuttgart.de (mxex1.tik.uni-stuttgart.de [129.69.192.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42A1930C34C for ; Mon, 22 Sep 2025 08:28:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=129.69.192.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758529741; cv=none; b=Mjl6qx09iitDMpSBQqBvyoodGAXz3tuNRYSBmAv2lmwXOJdqVoLRcA79Wj0bbzqZZ1APmb7g6VK9cqlWB85cD2MR8pKJ+l9zyTsMbMdM+0q2qQpUzn6KHcGdZBL1R0pzFkjqqR+M+rlB9QOkVxGzrBizWnIYYIhR97pD2dQLNp0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758529741; c=relaxed/simple; bh=7abNpAP6GuSyK9BKwk2mwIoPaKFBmuiAw5KXyNpBhYw=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dWEOdkGhb4jd7R8T8kgNuMkUrRAIK/BuQx3t9NRHO+BbtLPe+OwccSqpsJzo2ozNGyuMX8fcB8h0XDnC9u2Hhip/XBnd4Yi4NeQhAQb0RhCclfMymhSrT1CsQtdDj+x/fO5XZLPg6s4klSpY3mREWPS79fDmUXuk3kIUvRBtfis= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rus.uni-stuttgart.de; spf=pass smtp.mailfrom=rus.uni-stuttgart.de; dkim=pass (2048-bit key) header.d=uni-stuttgart.de header.i=@rus.uni-stuttgart.de header.b=DCfqSkEr; arc=none smtp.client-ip=129.69.192.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rus.uni-stuttgart.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rus.uni-stuttgart.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=uni-stuttgart.de header.i=@rus.uni-stuttgart.de header.b="DCfqSkEr" Received: from localhost (localhost [127.0.0.1]) by mxex1.tik.uni-stuttgart.de (Postfix) with ESMTP id 71B1E6104A for ; Mon, 22 Sep 2025 10:28:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=uni-stuttgart.de; h=x-mailer:user-agent:in-reply-to:content-disposition :content-type:content-type:mime-version:references:message-id :subject:subject:from:from:date:date; s=dkim; i= @rus.uni-stuttgart.de; t=1758529734; x=1760268535; bh=7abNpAP6Gu SyK9BKwk2mwIoPaKFBmuiAw5KXyNpBhYw=; b=DCfqSkErnqTNfnuiFST7hXfl7P F3Z58SFk/OQMr+/buHMzyBoEmE9j/fPjrzw+OSOJaHKIrxwc12bZUHbYqaXpyx8e cLe4yQIoqHttg+5hYgpzT1WbmtJTCGqbdVeeLRjjbZxznNwqjbO7xAx7ObXWoJzg Byaw4oXOMxHlLHRMEHmR8u80z8KQJ+aZ30+hM9g/kiYoP0bT7F3XnaWy13MkN2DO KxrbiueRRm3pl5nX/mCUVQD+cGrQ3IYOKekd6HKQrHY+nYy2Zpvgz6SJ2BbNc5a6 sWrxFaI+PS4H9n3ur4K5WvDJuK97mVS1j6Y95as+cv47y5goSYnt+60gwYjA== X-Virus-Scanned: USTUTT mailrelay AV services at mxex1.tik.uni-stuttgart.de Received: from mxex1.tik.uni-stuttgart.de ([127.0.0.1]) by localhost (mxex1.tik.uni-stuttgart.de [127.0.0.1]) (amavis, port 10031) with ESMTP id yC87vp5C2xwP for ; Mon, 22 Sep 2025 10:28:54 +0200 (CEST) Received: from authenticated client (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mxex1.tik.uni-stuttgart.de (Postfix) with ESMTPSA Date: Mon, 22 Sep 2025 10:28:54 +0200 From: Ulli Horlacher To: linux-btrfs Subject: Re: btrfs RAID5 or btrfs on md RAID5? Message-ID: <20250922082854.GD2624931@tik.uni-stuttgart.de> Mail-Followup-To: linux-btrfs References: <20250922070956.GA2624931@tik.uni-stuttgart.de> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Mailer: smtpsend-20240729 On Mon 2025-09-22 (17:11), Qu Wenruo wrote: > > Is btrfs RAID5 ready for production usage or shall I use non-RAID btrfs on > > top of a md RAID5? > > Neither is perfect. We live in a non-perfect world :-} > Btrfs RAID56 has no journal to protect against write hole. What does this mean? What is a write hole and want is the danger with it? > So you either run RAID5 for data only This is a mkfs.btrfs option? Shall I use "mkfs.btrfs -m dup" or "mkfs.btrfs -m raid1"? > and ran full scrub after every unexpected power loss (slow, and no > further writes until scrub is done, which is further maintanance burden). Ubuntu has (like most Linux distributions) systemd. How can I detect a previous power loss and force full scrub on booting? > Or just don't use RAID5 at all. You suggest btrfs RAID0? As I wrote: I have 4 x 4 TB SAS SSD (enterprise hardware, very reliable). Another disk layout option for me could be: 64 GB / filesystem RAID1 32 GB swap RAID1 3.9 TB /home 3.9 TB /data 3.9 TB /VM 3.9 TB /backup In case of a SSD damage failure I have to recover from (external) backup. -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlacher@tik.uni-stuttgart.de Allmandring 30a Tel: ++49-711-68565868 70569 Stuttgart (Germany) WWW: https://www.tik.uni-stuttgart.de/ REF: