If it was me, I would use a smaller drive for the OS (I was using a 160GB initially with my 1TB drives added for Greyhole storage). You can also partition the 1TB to separate the OS from data too prior to install.
Don't connect the 1TB drives until you have installed Fedora 14 and Amahi. I would recommend you not use LVM is you intend to use Greyhole. The wiki has guidance for installing Fedora 14 without LVM that works well.
http://wiki.amahi.org/index.php/Install_without_LVM
Once everything is installed and running, connect the 1TB drives. Follow the wiki guidance to add the drives to Amahi and the storage pool.
This is not the only way to do things, just my recommendation. Someone else might have better advice. This has worked well for me in the past. Keeps it simple.