I recently added a mirror to a very simple zfs pool and decided to document it here for posterity. This worked flawlessly in a FreeNAS 10 system with two 4 TB drives.
VMware VAAI Storage Array Support in Plain English
The most exciting enhancements in VMware vSphere 4.1 is the addition of vStorage API for Array Integration (VAAI). This new API allows VMware ESX to offload storage processing functions to capable storage arrays, reducing the workload on the server hardware in introducing new and exciting possibilities for performance and efficiency. VAAI in ESX 4.1 includes three separate capabilities: block zeroing, full copy, and hardware assisted locking.