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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 81C34C432C0 for ; Sun, 17 Nov 2019 18:49:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A8B52075C for ; Sun, 17 Nov 2019 18:49:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726203AbfKQStb (ORCPT ); Sun, 17 Nov 2019 13:49:31 -0500 Received: from dc2.fullpliant.org ([213.186.44.166]:45266 "HELO dc2.fullpliant.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726067AbfKQStb (ORCPT ); Sun, 17 Nov 2019 13:49:31 -0500 Date: Sun, 17 Nov 2019 19:49:07 +0000 From: Hubert Tonneau To: Goffredo Baroncelli Cc: linux-btrfs@vger.kernel.org Subject: Re: Avoiding BRTFS RAID5 write hole Message-ID: In-Reply-To: References: <0JGAX5Q12@briare1.fullpliant.org> <7723feea-c3cd-b1eb-b882-aa782bbc6e2a@libero.it> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Goffredo Baroncelli wrote: > > You are suggesting to keep the "hot" data in a RAID1 block group, and write/update the RAID5 block group only when the data is "cold" in the RAID1 cache. That's it. Just remove the last word 'cache' because in some cases, the data might also remain as RAID1 forever, as an exemple if the nocow flag is set and the partition has enough free space. Regards, Hubert Tonneau