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=DKIM_SIGNED,DKIM_VALID, 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 A75ACCA9EAD for ; Sun, 20 Oct 2019 21:44:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 731E921929 for ; Sun, 20 Oct 2019 21:44:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=colorremedies-com.20150623.gappssmtp.com header.i=@colorremedies-com.20150623.gappssmtp.com header.b="QxPmV/Rr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726526AbfJTVoM (ORCPT ); Sun, 20 Oct 2019 17:44:12 -0400 Received: from mail-wr1-f47.google.com ([209.85.221.47]:41347 "EHLO mail-wr1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726374AbfJTVoM (ORCPT ); Sun, 20 Oct 2019 17:44:12 -0400 Received: by mail-wr1-f47.google.com with SMTP id p4so11604102wrm.8 for ; Sun, 20 Oct 2019 14:44:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=colorremedies-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=H+yHy0dyq7QZMnnboJ0/RrF+o/h5SxLwNqZhC+Pn/+8=; b=QxPmV/RrRTyK6dVQF1h5S6q8QPhMTt0V13A0hBgpsfd2pJkOF/OHwbxF7NI/jHhDcx oDqaxL6X6zNG1JuMeL2gJJNBqblFJCCnN7P1qdgJFLJkme+Fb4yrOm/GYG2RKr/aV8Ss 1PgXBhYZGhbqgdLqKc5oHU87L2QuGKiqsj531ix38wAaOmgZ4KwPU2a8L4qbqpO+8d51 UeItsxRV91jKcJol9VjE3rMZnYb6ypamh5Z3QOJdSi3GixGlMEzbPOdDEbdjsnV0xjNO zcouxA/N8MwwUjrIuBFtnOPHIPi6iqFUCDE7jtMYVP+Xed5GxzLQ4NbYLTgQ8GzK6TxU j+9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=H+yHy0dyq7QZMnnboJ0/RrF+o/h5SxLwNqZhC+Pn/+8=; b=LR4004nqDQSkPpzhDMIVhxVsqh5VvrdkOdR2WAHZ4rd9MdQyTpl2bv+uBJFinIjDAk iYlGPLCskbjLjJIO9l65YdmfV0REKbrk+1LH18MRjJjZugGKEBjMerEPSmfzHvAHY11V pZtoGPVlWC78tyaLcDmhCLYLAfST/M6i9dP3FXY8xY7y3dL0vcz/YOD6OGjWYMsfH8Ul n+U1yN0eZXxQud/n10mqjg+7nayfgL+QLqaQl4QRy3lE+2DTPgOTEDjAqsnQ9Ix6755G yfZiEYQLesepatyHaG6YSpHdesjNYqJADZvFXbWc2o/0nBCjuzcPadikYeZn+gTdYpkn bdag== X-Gm-Message-State: APjAAAWo80R3Pmx4gCC0C/Ip10p73bYkYj0G37x7Au4WFg0QOKn6pPls Pz4OpCnUMF9yD3BCnU55Z0c5+0kjeTmo3lI4SPSmGg== X-Google-Smtp-Source: APXvYqw5rK5cZg9f6V5Bs6zWkgq6opOpUWNpjxRajmpp5iq3wb+trIcXX4l1R60ezs+5YrpNXYFWiet+Rbv+YHrj5ZQ= X-Received: by 2002:a5d:4a8a:: with SMTP id o10mr946317wrq.101.1571607850302; Sun, 20 Oct 2019 14:44:10 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Chris Murphy Date: Sun, 20 Oct 2019 23:43:52 +0200 Message-ID: Subject: Re: MD RAID 5/6 vs BTRFS RAID 5/6 To: Supercilious Dude Cc: Chris Murphy , Btrfs BTRFS , Qu Wenruo Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Sat, Oct 19, 2019 at 12:18 AM Supercilious Dude wrote: > > It would be be useful to have the ability to scrub only the metadata. In = many cases the data is so large that a full scrub is not feasible. In my "l= ittle" test system of 34TB a full scrub takes many hours and the IOPS satur= ate the disks to the extent that the volume is unusable due to the high lat= encies. Ideally there should be a way to rate limit the scrub operation so = that it can happen in the background without impacting the normal workload. In effect a 'btrfs check' is a read only scrub of metadata, as all metadata is needed to be read for that. Of course it's more expensive than just confirm checksums are OK, because it's also doing a bunch of sanity and logical tests that take much longer. --=20 Chris Murphy