Some Tablo models (like the Tablo DUAL 128GB and Tablo QUAD 1TB) are designed to work directly out of the box, without any external storage required.
This means you can watch Live TV or schedule airings without connecting any external hard drive.
Tablo will store the recordings on its own 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 and format an external storage device, you will still be able to play and delete recordings on the internal storage but all new recordings will be sent to the newer, external storage you have attached.
You cannot use more than one type of storage, or more than one hard drive at the same time.