Btrfs v0.19 Brings Some Gains, Some Losses
When upping the size to 4GB, the write performance continued to be better under Btrfs v0.19, but by a much smaller lead. The difference here was 40MB/s versus 43MB/s.
While the 4GB write performance was better with the new Btrfs release, the 4GB read performance had a noticeable degradation in its performance. The average read speed had dropped from 147MB/s with Btrfs v0.18 in Linux 2.6.30 to 126MB/s with Btrfs v0.19 in Linux 2.6.31. This is about a 14% drop in the disk's read performance.
Turning to Dbench with just one active client, Btrfs v0.19 had brought a small speed-up in performance with this test profile. Btrfs v0.18 had an average speed of 19.76MB/s while Btrfs v0.19 had a speed of 23.73MB/s.