We doubled the test size again to 8GB and here the EXT4 file-system delivered better write performance than Btrfs. The average speed here for EXT4 was 75MB/s while Btrfs was at 61MB/s, just 2MB/s faster than EXT3. XFS was in front by a small lead.
Btrfs had the lead when it came to the 4GB read performance with IOzone, but at 8GB, Btrfs had lost its lead slightly. In fact, EXT3 delivered the best performance but the EXT4 and Btrfs file-systems were in a dead-heat. Here the XFS file-system was significantly slower than the other three file-systems tested.
The EXT4 file-system had delivered better performance than Btrfs with Dbench when only using one client. The XFS file-system was almost twice as fast as Btrfs.