Storage expansion

I currently have a Dell R520 server with 8 bays full of 2TB hard drives. I have more 2TB hard drives I can use. Looking for suggestions to expand my current setup. Currently have FreeNAS. Thanks!

With freenas the only option you have is to create a pool that is mirrored with your 2 drives. If you had 8 more bays drives you could extend your storage then but, freenas as it sits cannot extend storage a drive at a time. It has to match the current array. basically a stripe.

Any suggestions on hardware to make another pool out of?