I am building a new server that will have ALOT of harddrive space. My original plan was to simply install FreeNas and forget about it. But then I I realized that perhaps I could instead virtualize FreeNas allowing me to also use the server for more than just file backups but also server testing (LAMP, etc). However I am not sure on the best approach for this.

12TB drive pool + 32GB SSD for system.

On idea was to install Ubuntu 12.04 LTS with VirtualBox then Run FreeNas as a virtual guest (on the SSD). How would I then give freenas access to the drive pool? Would Ubuntu need something like ZFS to be installed and then just created dynamic virtual disks in FreeNas?

Someone at work recommended something like Xen hypervisor.

My Goals:
Build capable backup solution for my home network.
Create testing environmental for multiple OS systems.
Each of these solutions should not be co-mingled. (I.E. Installing Ubuntu + Samba + ZFS + apache + MYSQL+ blahhaa all in the same environment)