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 60033C433F5 for ; Fri, 13 May 2022 15:23:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381941AbiEMPXP convert rfc822-to-8bit (ORCPT ); Fri, 13 May 2022 11:23:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381922AbiEMPXO (ORCPT ); Fri, 13 May 2022 11:23:14 -0400 X-Greylist: delayed 525 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Fri, 13 May 2022 08:23:11 PDT Received: from ste-pvt-msa1.bahnhof.se (ste-pvt-msa1.bahnhof.se [213.80.101.70]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 855E463BC5 for ; Fri, 13 May 2022 08:23:09 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by ste-pvt-msa1.bahnhof.se (Postfix) with ESMTP id A11ED3F60E; Fri, 13 May 2022 17:14:22 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from ste-pvt-msa1.bahnhof.se ([127.0.0.1]) by localhost (ste-pvt-msa1.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tK8zAPTX7z1G; Fri, 13 May 2022 17:14:21 +0200 (CEST) Received: by ste-pvt-msa1.bahnhof.se (Postfix) with ESMTPA id D54F63F36E; Fri, 13 May 2022 17:14:21 +0200 (CEST) Received: from [192.168.0.126] (port=60920) by tnonline.net with esmtpsa (TLS1.3) tls TLS_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1npWzq-0002d9-2y; Fri, 13 May 2022 17:14:20 +0200 Date: Fri, 13 May 2022 17:14:21 +0200 (GMT+02:00) From: Forza To: Qu Wenruo , linux-btrfs@vger.kernel.org Message-ID: In-Reply-To: References: Subject: Re: [PATCH 0/4] btrfs: cleanups and preparation for the incoming RAID56J features MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Mailer: R2Mail2 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Hi, ---- From: Qu Wenruo -- Sent: 2022-05-13 - 10:34 ---- > Since I'm going to introduce two new chunk profiles, RAID5J and RAID6J > (J for journal), Great to see work being done on the RAID56 parts of Btrfs. :) I am just a user of btrfs and don't have the full understanding of the internals, but it makes me a little curious that we choose to use journals and RMW instead of a CoW solution to solve the write hole. Since we need on-disk changes to implement it, could it not be better to rethink the raid56 modes and implement a solution with full CoW, such as variable stripe extents etc? It is likely much more work, but could have better performance because it avoids double writes and RMW cycles too. Thanks Forza