From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:27279 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932815AbcCOWTs (ORCPT ); Tue, 15 Mar 2016 18:19:48 -0400 Subject: Re: Incompat features: raid56 ... when creating a RAID6? To: Andreas Grosse References: <16570443.SxVegaKaET@andilaptop> From: Anand Jain Cc: linux-btrfs@vger.kernel.org Message-ID: <56E88A7C.1010801@oracle.com> Date: Wed, 16 Mar 2016 06:19:40 +0800 MIME-Version: 1.0 In-Reply-To: <16570443.SxVegaKaET@andilaptop> Content-Type: text/plain; charset=windows-1252; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 03/16/2016 05:42 AM, Andreas Grosse wrote: > Hello everyone! > > I just wanted to create a RAID6 and got the following output: > >> # mkfs.btrfs -d raid6 -m raid6 -L slowPool /dev/sd[cdefgh] >> btrfs-progs v4.4.1 >> See http://btrfs.wiki.kernel.org for more information. >> >> Label: slowPool >> UUID: 85ddf6a7-51f1-4cc0-b6cd-d472277b0e86 >> Node size: 16384 >> Sector size: 4096 >> Filesystem size: 27.29TiB >> >> Block group profiles: >> Data: RAID6 4.01GiB >> Metadata: RAID6 4.01GiB >> System: RAID6 14.50MiB >> >> SSD detected: no >> Incompat features: extref, raid56, skinny-metadata >> Number of devices: 6 >> >> Devices: >> ID SIZE PATH >> >> 1 4.55TiB /dev/sdc >> 2 4.55TiB /dev/sdd >> 3 4.55TiB /dev/sde >> 4 4.55TiB /dev/sdf >> 5 4.55TiB /dev/sdg >> 6 4.55TiB /dev/sdh > > And then the line saying "Incompat features: ... raid56" came to my eyes. > Reading the corresponding manpage, it says: >> raid56 >> extended format for RAID5/6, also enabled if raid5 or raid6 block groups >> are selected > > So why is raid56 marked as incompatible if I just created a file system with > multiple disks using the RAID6 profile? Have I misunderstood something there? > I am confused. Can somebody here lighten this up? Those messages are indeed confusing. It just indicates the FS may fail to mount on certain older kernels. Not necessarily the kernel in the system on which you ran btrfs-progs. Sorry that it not very obvious at the moment, but there are patches to make this part better. To check features that your running kernel supports you could use ls /sys/fs/btrfs/features But note: Some of the names used by sys/fs/..features don't exactly match with the names used by btrfs-progs: incompatible.. (a bug, which is also fixed in the patch). Thanks, Anand > (If important: Gentoo Linux with kernel 4.5.0, btrfs-progs v4.4.1) > > AndiNrybXǧv^)޺{.n+{n߲)w*jgݢj/zޖ2ޙ&)ߡaGhj:+vw٥ >