From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f43.google.com ([209.85.214.43]:35769 "EHLO mail-it0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753605AbdGXNqg (ORCPT ); Mon, 24 Jul 2017 09:46:36 -0400 Received: by mail-it0-f43.google.com with SMTP id h199so34508527ith.0 for ; Mon, 24 Jul 2017 06:46:36 -0700 (PDT) Subject: Re: Best Practice: Add new device to RAID1 pool To: Cloud Admin , linux-btrfs@vger.kernel.org References: <1500895655.2781.6.camel@cloud.haefemeier.eu> From: "Austin S. Hemmelgarn" Message-ID: <18d96f74-00a8-9bb9-dddc-f50940d0971e@gmail.com> Date: Mon, 24 Jul 2017 09:46:34 -0400 MIME-Version: 1.0 In-Reply-To: <1500895655.2781.6.camel@cloud.haefemeier.eu> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2017-07-24 07:27, Cloud Admin wrote: > Hi, > I have a multi-device pool (three discs) as RAID1. Now I want to add a > new disc to increase the pool. I followed the description on https://bt > rfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices and > used 'btrfs add '. After that I called a balance > for rebalancing the RAID1 using 'btrfs balance start '. > Is that anything or should I need to call a resize (for example) or > anything else? Or do I need to specify filter/profile parameters for > balancing? > I am a little bit confused because the balance command is running since > 12 hours and only 3GB of data are touched. This would mean the whole > balance process (new disc has 8TB) would run a long, long time... and > is using one cpu by 100%. Based on what you're saying, it sounds like you've either run into a bug, or have a huge number of snapshots on this filesystem. What you described is exactly what you should be doing when expanding an array (add the device, then run a full balance). The fact that it's taking this long isn't normal, unless you have very slow storage devices.