10 times higher disk load with btrfs

[Stefan Priebe <s.priebe@profihost.ag>]

Hi devs,

while btrfs is now declared as stable ;-) i wanted to retest btrfs on 
our production cluster on 2 out of 54 osds. So if they crash it doesn't 
hurt.

While if those OSDs run XFS have spikes of 20MB/s every 4-7s. The same 
OSDs after formatting them with btrfs have spikes of 190MB/s every 4-7s.

Why does just another filesystem raises the disk load by a factor of 10?

I'm running dumpling.

Greets Stefan