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)
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