Oracle ZFS is very fast and it is efficient. It has outperformed any hardware array controller that I've ever come across. With Oracle ZFS on my NAS, which is running five, four terabyte drives, when I've had a drive failure and changed one out, it'll rebuild that array in two hours, or maybe less. When you think you're rebuilding almost four terabytes of data redundancy, that's pretty good using an old AMD Turion hardware, that's nothing to complain about.
