Cant mount xfs lvm. Experimental Features?

[Marko Weber|8000]

dave,

Am 2015-08-25 13:54, schrieb Dave Chinner:
> On Tue, Aug 25, 2015 at 10:25:16AM +0200, Marko Weber|8000 wrote:
>> 
>> Hello List, Hello Dave...
>> 
>> 
>> i try to mount on my backup server an Lvm Partition and get errors
>> in stdout and log:
>> 
>> /var/log/messages:
>> 
>> Aug 25 10:20:31 backupserver kernel: XFS (dm-2): Version 5
>> superblock detected. This kernel has EXPERIMENTAL support enabled!
>> Aug 25 10:20:31 backupserver kernel: Use of these features in this
>> kernel is at your own risk!
>> Aug 25 10:20:31 backupserver kernel: XFS (dm-2): Superblock has
>> unknown read-only compatible features (0x1) enabled.
>> Aug 25 10:20:31 backupserver kernel: XFS (dm-2): Attempted to mount
>> read-only compatible filesystem read-write.
>> Aug 25 10:20:31 backupserver kernel: Filesystem can only be safely
>> mounted read only.
>> Aug 25 10:20:31 backupserver kernel: XFS (dm-2): SB validate failed
>> with error 22.
> 
> You need to run the same version kernel on both servers. The primary
> has a more recent kernel and feature set than your older backup
> server is running.
> 
> Cheers,
> 
> Dave.

you was right.
There was new kernel built. /usr/src/linux pointed to new kernel source.
But machine was not rebooted. So kernel version before kernel built was 
loaded.
I rebooted machine.
i renoved logical volume
i created logical volume
i tried to mount it and get:

Aug 25 18:43:15 backupserver kernel: md4: unknown partition table
Aug 25 18:43:15 backupserver syslog-ng[1417]: Internal error, 
alarm_set() called while an alarm is still active;
Aug 25 18:43:56 backupserver kernel: md4: unknown partition table
Aug 25 18:44:01 backupserver kernel: XFS (dm-2): Invalid superblock 
magic number

pvdisplay shows:

# pvdisplay
   --- Physical volume ---
   PV Name               /dev/md4
   VG Name               VolGroup01
   PV Size               2.69 TiB / not usable 1.25 MiB


so what is XFS missing?