I would be good practice to create at least /tmp, /var, /usr and /boot as well. You could also use lvm to manage your physical disks. This would let you be conservative on the partition sizes and grow them as needed. When you add disks down the road, you can simply add it to the logical volume and grow the filesystems as necessary.
XFS or JFS would be ideal for the partition that stores your recordings as they handle large files better than ext3 or reiser (both good for smaller files or large directories). All of those filesystems can be grown while only some can be shrunk (reiser for sure, not sure about the rest).