Also, note that ZFS spawns a lot of threads for concurrent IO. So, enable NCQ (check queue length in /sys/block/<drive>/queue/nr_requests) on the drives if it is not set already. Invest into some SSD drive(s) as the L2 cache, which will speed up random IO ops tremendously.
At first I just wanted to see how much work it would take to port ZFS to FreeBSD. I started by making it compile on FreeBSD, and once I did that, I was quite sure it would take at least six months to have the first prototype working. The funny thing was that after another week or so, ZFS was running on my test machine