Phoronix: Btrfs In 2014: RAID5/RAID6, Data Deduplication
Samsung's F2FS isn't the only Linux file-system receiving new features but the Btrfs developers are currently baking some new treats of their own...
It would be pretty interesting to see some benchmarks of btrfs+bcache with various SSD optimizations enabled. Apparently the default behaviour is that btrfs detects the SSD and enables them, but bcache then sends sequential writes straight to the spinning rust. 
Who in their right mind use RAID5? I think it is better if they focus on RAID6 and shoot for triple-parity RAID instead.