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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0867C28D13 for ; Fri, 19 Aug 2022 22:38:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242238AbiHSWiY (ORCPT ); Fri, 19 Aug 2022 18:38:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239270AbiHSWiW (ORCPT ); Fri, 19 Aug 2022 18:38:22 -0400 Received: from wout4-smtp.messagingengine.com (wout4-smtp.messagingengine.com [64.147.123.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE6CB2CDD8 for ; Fri, 19 Aug 2022 15:38:21 -0700 (PDT) Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailout.west.internal (Postfix) with ESMTP id C3BFF32002F9; Fri, 19 Aug 2022 18:38:20 -0400 (EDT) Received: from imap52 ([10.202.2.102]) by compute5.internal (MEProxy); Fri, 19 Aug 2022 18:38:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shamm.as; h=cc :cc:content-type:date:date:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to; s=fm2; t=1660948700; x=1661035100; bh=rq6RrsY01S gMUm6XwMnMU6xCgfoJMCwLI6nIYh/O3tI=; b=Z1dya6mnOB0kvu5TUagYyZ8QKd qdrP3nGVWE92ckL3XuUvFMnAbO692SO8ubuotJ3HUM6uCt2rscq3nF2aUhsXdAF2 H+FNWzQANk0xyu5ZAyoRSHwr3nyT1GrXPNoEtAgzbSTtcuRVXrjez4JUAZyhRJjv p0cui7KDBBF6IZaNxac9RJlFGJ0Gxv5WD9H3+lCkbL+isi3xKU3NDnAr352maHoY vjCzK0dv/We7y35gJCCjgIt2/BpV2HvXKAaa8+Wcdlan/JTZB3Ty0YGOpfasPMO2 MPJ6qbKgxUA8V1Z/iEgWg04EJ73h69/m8b9yWHvB6bfODY24zibdbu8Nb5Dw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:date:date:feedback-id :feedback-id:from:from:in-reply-to:in-reply-to:message-id :mime-version:references:reply-to:sender:subject:subject:to:to :x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm1; t=1660948700; x=1661035100; bh=rq6RrsY01SgMUm6XwMnMU6xCgfoJ MCwLI6nIYh/O3tI=; b=SJ2R9o6jI/wcXI6XcNbXRKBjheWcVEAPHr7gEGJlVtg4 JlziQuv0ZZb9xGatNUvgAxxKAEiOzsFqIs8o0SEbF3473soZFZQFHc2HbNqNyGX/ fKM3PoJQacbPHn4DBxWQofd/ujZV/GlS7iHSXbtjDSyyHi1qJ9bu0PLlkfO7ogme BbhnvZ15mZX+k222UFMs0HHrWmsdOA16lRvqcVXOY0eELBqifF79WTnrekLN9Tl1 7GpKFraEqs9WlMgOaIW85yP5lDfsG92pCr4tkpCxH0EwIGMdzTKUWe++uHeeOPC5 o51fE0CPNnuVIla92yAh9vkB4bb8JZC/n/XFsLOKcA== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvfedrvdeivddgudefucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepofgfggfkjghffffhvfevufgtsehttdertderredtnecuhfhrohhmpedfifgv ohhrghgvucfuhhgrmhhmrghsfdcuoegsthhrfhhssehshhgrmhhmrdgrsheqnecuggftrf grthhtvghrnhepgedvheeuffeitddvvddvhefhhfeujeehkeeluefgudegvefhkeeukeeu geefudeinecuffhomhgrihhnpegsthhrfhhsrdhithenucevlhhushhtvghrufhiiigvpe dtnecurfgrrhgrmhepmhgrihhlfhhrohhmpegsthhrfhhssehshhgrmhhmrdgrsh X-ME-Proxy: Feedback-ID: i1ac146fc:Fastmail Received: by mailuser.nyi.internal (Postfix, from userid 501) id 042ABC6008B; Fri, 19 Aug 2022 18:38:20 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-841-g7899e99a45-fm-20220811.002-g7899e99a Mime-Version: 1.0 Message-Id: <6b835970-07c9-4b8c-a686-57776f494db8@www.fastmail.com> In-Reply-To: <1a102e00-144c-43c8-bb08-7bdb4072d056@www.fastmail.com> References: <87v8qokryt.fsf@vps.thesusis.net> <1a102e00-144c-43c8-bb08-7bdb4072d056@www.fastmail.com> Date: Fri, 19 Aug 2022 18:37:46 -0400 From: "George Shammas" To: "Chris Murphy" , "Phillip Susi" Cc: "Btrfs BTRFS" Subject: Re: What exactly is BTRFS Raid 10? Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Aug 19, 2022, at 6:18 PM, Chris Murphy wrote: > man mkfs.btrfs explains some of this. Minimum devices 2. My first mail included a link the the man page of mkfs.btrfs. It is devoid of information of raid10 other than it is an option. > And keep in mind all btrfs raid is at the chunk level. Not block device > level. So there's no such thing as a mirrored device, but rather > mirrored chunks (two copies of a block group on separate block devices). > > And yes, you can only lose one device with btrfs raid10. And this is exactly why I am asking this question. Given that - both raid1 and raid10 can only tolerate a single disk failure - chucks are placed evenly across drives, effectively making files striped even if the chucks themselves are not striped. It seems that both "raid1" and "raid10" are functionally equivalent in btrfs. Or there is a nuance that I'm missing and is not documented. These gotchas are not obvious to me, even after 12 years of working with traditional raid setups. Perhaps raid1 does not require that chucks are placed evenly, allowing for hotspots? In which case raid10 is almost always preferable unless you have disks of unequal size? There needs to be some authoritative text on the differences and pros/cons btrfs raid1 and btrfs raid10, especially since raid5/6 are not recommended. --George