The best test is to do what you want to do. Install the drive, create a pool, copy data to it (preferably with some type of checksum). Copy the data back (different location). Create a new checksum. Compare checksums. Of course that doesn't tell you if there's some strange bug like only being able to access 2.3GB of the 3TB drive, but the ZPOOL status should tell you if it's really seeing all your space.