Add another disk as RAID once the first contains data

[bsbtreet]

I may be interested in purchasing a device with QuTS hero (ZFS) or with the QTS simpler version. But I have a doubt:
What happens if I put a single 18TB disk into the device, and a few months later I purchase another disk of the same exact size and model, can I add it to the pool so the contents of the first are also added to the second (like a RAID 1)? Or must I do it from the beginning and purchase the 2 disks right away? Does it depend if it's QTS or QuTS?

[P3R]

It depend on what OS is used. In QTS it's possible but not in QuTS Hero.