According to the Microsoft Building Windows 8 Blog, storage spaces are not bootable. They allude to being able to put the bootloader elsewhere, but that's not easily done from in the installer (and details are lacking as of this writing). Doesn't look like it would help you anyway, given that you only have the two drives.
Q) Can I boot from a space?
In Windows 8, you cannot boot from a space. As an alternative, you can continue to use dynamic volumes for booting. At release, we will offer guidance on how you can add appropriately partitioned system/boot disks (with dynamic volumes) to a pool.