Starting with the Apache server benchmark, using ZFS-FUSE causes a dramatic performance hit compared to EXT4 and Btrfs. The number of requests that could be sustained per second when using ZFS-FUSE on Ubuntu Linux was 42% lower than using EXT4, which is the default file-system of Ubuntu Lucid Lynx.
The EXT4 performance under the PostgreSQL workload was over six times faster than when the ZFS file-system had been tested in the Linux user-space. The latest ZFS-FUSE Git code for the upcoming ZFS-FUSE 0.7 release did improve the performance by 6% over ZFS-FUSE 0.6.9, but obviously, this made no dent in the EXT4 performance. Interestingly, the ZFS-FUSE performance was actually faster than that of Btrfs, but it's known right now that the PostgreSQL server performance is notoriously bad right now for Btrfs. We were able to successfully run this test profile under OpenSolaris b134 on ZFS and its performance was 61% faster than the ZFS-FUSE Git code on Linux.
The PostgreSQL disk performance was over six times faster than ZFS-FUSE compared to EXT4, but with the PostMark e-mail server disk benchmark the performance lead was greater by nine times. ZFS on OpenSolaris was two times faster than ZFS-FUSE 0.6.9 and just under two times for ZFS on OpenSolaris b134. While ZFS is designed around OpenSolaris, it still only ran at 31% the speed of Btrfs and just 22% the speed of EXT4.