Yes, you can go ahead and build a NAS. Using the Banana Pi M2 Berry. It's a small computer that can handle basic NAS tasks. To connect a larger hard drive, you'll need to provide power to it separately. The operating system called Armbian, which is designed for devices like the Banana Pi M2 Berry, should work without needing any manual adjustments. However, it's always a good idea to check the compatibility and support forums to make sure everything will work smoothly. Good luck with your NAS project.