Good for the new tesla buyers on Sentry and DashCam videos.
Non-tesla buyers, please be easy on the post.
Detail storage usage quote from website tesladriver:
Required amounts of data on the USB flash drive
The video recordings of the Tesla sentry mode and the dashcam function are stored on a USB flash drive. The drive must be connected to one of the two front USB ports in the car. With dashcam and sentry mode, the footage from the front camera, the two side-facing rear cameras and the rear camera footage is recorded. One minute of image recording requires 30 MB of memory per camera. Since the Dashcam only stores 60 minutes while driving and then overwrites the oldest data, the following space is required for the Dashcam function on the USB devices:
60 minutes * 30 MB * 4 cameras = ~7200 MB (=7.1 GB) for one hour of continuous recording of the Dashcam. More data is not needed for the Dashcam. Videos older than one hour will be overwritten.
Sentry mode (per event)
10 minutes * 30 MB * 4 cameras = ~1200 MB (=1.2 GB) for a manual 10-minute recording by pressing the Dashcam button.
Sentry mode also stores 10 minutes of video from the four cameras per threat detected. This means 1200 MB per event. So, a USB stick that is too small can get full quickly. The stored videos of the sentry mode cannot be deleted individually in the vehicle. The oldest sentry videos are automatically overwritten when the stick is full.