The Tablo DUAL is designed to work directly out of the box, without any external storage required. Simply attach power and your OTA antenna (and Ethernet, if you wish, otherwise you can use Tablo over Wi-Fi), and your Tablo will guide you through the setup.
Directly out of the box, you can watch Live TV or schedule airings to be recorded right away. Tablo will store the recordings on its own 64GB of internal storage. You can watch the recordings directly from the internal storage at any time. The Tablo Settings screen will show you how much space is available on the internal storage.
If/when you attach an external storage device, you will still be able to play and delete recordings on the internal storage. All new recordings will be sent to the newer, external storage you have attached.