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 078652ECE86 for ; Mon, 20 Oct 2025 09:07:20 +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=1760951245; cv=none; b=Md0Xl9UMyrN2a2gi+0T6cbgLX3Km1zLCBwySlxz7W6Cso3YYi0U3MHRnbk3oU8cwNqO2phgHCQRKJEevbLyY6UbGD6m8CpY/lBdoM2s+ZDhQyy1d21qga0GixMR381PMJH3nzF4+osGDObHxY6DA2f5sjSlJM0BUePBynQz1TOA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760951245; c=relaxed/simple; bh=GG+W9pv6EOqicX5kEEPMO7LYfX5TEDr04gY0ErV+4Cc=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OtTQmYA4gNBj+8H+hOjkj9tdfRQOXIY/OC/I1wA8Q9J6vM3Pwz8kcyK7qoL6lHTMeF6iHYhNaLfvOkdgiWwblmoW55E5Rdyc+AYJgSDIGua5byGovW8Z+8FXNqyKDnSNZGMtbomkuNhKpC89AcpdIdB3KXNzMzTBlLe4G1wRbGc= 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=aqHGXmND; 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="aqHGXmND" Received: from localhost (localhost [127.0.0.1]) by mxex1.tik.uni-stuttgart.de (Postfix) with ESMTP id 429CB60B6C for ; Mon, 20 Oct 2025 11:00:20 +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=1760950818; x=1762689619; bh=GG+W9pv6EO qicX5kEEPMO7LYfX5TEDr04gY0ErV+4Cc=; b=aqHGXmNDCWyH/jRCLKJNHHGwC9 OetD+C6dixeYEY1n566SEdrZhSnH7bQJBoM3IzjkvI+Aa4zvdxowNrCdAFGI0gHp FGCd31zujOOI1SEvAKVKkh+xaVyl2Vg5+M0q/l9K9rQSRdZa2VLDj99Xh7ggK7pp z1m8YvRByB2GxbDoArfxmY4j54koFcv1h3fq4S3imnJeIHN35ByqXG3yt6qs+wWF LnhDS8gRvTMmU7MUWCYO4v7LLbnxlCtvhTP9nFnPoWtZ8GkzASIcM2qNRO3C+pqr IYvJ0R4kfqIze8kJdKVzSFyZZUWUXc7TtZ1hO6FYpSJOXTJyVWlVxCGCV+Dg== 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 Y7-x7CZKSZUN for ; Mon, 20 Oct 2025 11:00:18 +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, 20 Oct 2025 11:00:18 +0200 From: Ulli Horlacher To: linux-btrfs Subject: Re: btrfs RAID5 or btrfs on md RAID5? Message-ID: <20251020090018.GA1446208@tik.uni-stuttgart.de> Mail-Followup-To: linux-btrfs References: <20250922070956.GA2624931@tik.uni-stuttgart.de> <20250922082854.GD2624931@tik.uni-stuttgart.de> <95ece5d8-0e5a-4db9-8603-c819980c3a3b@suse.com> <20250922092300.GA2634184@tik.uni-stuttgart.de> <1e4baff2-1310-437a-be62-5e9b72784a54@gmx.com> 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: <1e4baff2-1310-437a-be62-5e9b72784a54@gmx.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Mailer: smtpsend-20240729 Resuming this discussion... On Mon 2025-09-22 (18:57), Qu Wenruo wrote: > >>>> 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"? > >> > >> For RAID5, RAID1 is preferred for data. > > > > Then the real usable capacity of this volume is only the half? > > No, metadata is really a small part of the fs. > > The majority of usable space really depends on the data profile. > > If you use RAID1 metadata + RAID5 data, I believe only less than 10% of > real space is used on RAID1, the remaining is still RAID5. Sounds like a good compromise solution! Asuming I have 4 partitions with equal size, then the suggested command to create the filesystem would be: mkfs.btrfs -m raid1 -d raid5 /dev/sda4 /dev/sdb4 /dev/sdc4 /dev/sdd4 Does this setup help to protect against write hole? -- 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:<1e4baff2-1310-437a-be62-5e9b72784a54@gmx.com>