Question. Is drive extender just a way of managing drive pooling?

Forgive any lack of proper terms as I'm researching things as I type this up.

If MS really does get rid of DE in vail, I'm thinking I might go into more of a free route for my server "needs" once I outgrow my HP WHS. FreeNAS looks interesting (and there's 256megs of hidden usb flash on the EX47x I didn't know about that can host FreeNAS????), but I know next to nothing of it. Apparently it natively supports ZFS, which supports drive pooling? Am I right in that? I don't know. I came across this comment on a random board about it all.

"Derek said... @ May 15, 2010 10:11 AM

    The drive pool is fixed in at least the latest (maybe earlier version too?) FreeNAS. FreeNAS now natively supports Sun's ZFS, so you can use that for media storage and add drives too the zPool as needed. I haven't used it yet, but I plan to do something similar to your previous article with the ZFS trick. I think the UPnP has come a long way since then too."

Can anyone educate me a bit on all this? I've got a spare dual-core machine that I could experiment on, but I don't have any spare drive(s) to plug into it and play with, thus negating my desire to do something new and neat.