From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from www.zeus06.de ([194.117.254.36]:38334 "EHLO mail.zeus06.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751320AbbKYLnO (ORCPT ); Wed, 25 Nov 2015 06:43:14 -0500 To: linux-btrfs@vger.kernel.org From: Mario Subject: Imbalanced RAID1 with three unequal disks Message-ID: <56559D40.9050305@kicherer.org> Date: Wed, 25 Nov 2015 12:36:32 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi, I pushed a subvolume using send/receive to an 8 TB disk, added two 4 TB disks and started a balance with conversion to RAID1. Afterwards, I got the following: Total devices 3 FS bytes used 5.40TiB devid 1 size 7.28TiB used 4.54TiB path /dev/mapper/yellow4 devid 2 size 3.64TiB used 3.17TiB path /dev/mapper/yellow1 devid 3 size 3.64TiB used 3.17TiB path /dev/mapper/yellow2 Btrfs v3.17 Data, RAID1: total=5.43TiB, used=5.39TiB System, RAID1: total=64.00MiB, used=800.00KiB Metadata, RAID1: total=14.00GiB, used=5.55GiB GlobalReserve, single: total=512.00MiB, used=0.00B In my understanding, the data isn't properly balanced and I only get around 5.9TB of usable space. As suggested in #btrfs, I started a second balance without filters and got this: Total devices 3 FS bytes used 5.40TiB devid 1 size 7.28TiB used 5.41TiB path /dev/mapper/yellow4 devid 2 size 3.64TiB used 2.71TiB path /dev/mapper/yellow1 devid 3 size 3.64TiB used 2.71TiB path /dev/mapper/yellow2 Data, RAID1: total=5.41TiB, used=5.39TiB System, RAID1: total=32.00MiB, used=784.00KiB Metadata, RAID1: total=7.00GiB, used=5.54GiB GlobalReserve, single: total=512.00MiB, used=0.00B /dev/mapper/yellow4 7,3T 5,4T 969G 86% /mnt/yellow Now, I get 6.3TB of usable space but, in my understand, I should get around 7.28 TB or am I missing something here? Also, a second balance shouldn't change the data distribution, right? I'm using kernel v4.3 with a patch [1] from kernel bugzilla [2] for the 8 TB SMR drive. The send/receive of a 5 TB subvolume worked flawlessly with the patch. Without, I got a lot of errors in dmesg within the first 200GB of transferred data. The OS is a x86_64 Ubuntu 15.04. Thank you! Mario [1] http://git.kernel.org/cgit/linux/kernel/git/mkp/linux.git/commit/?h=bugzilla-93581&id=7c4fbd50bfece00abf529bc96ac989dd2bb83ca4 [2] https://bugzilla.kernel.org/show_bug.cgi?id=93581