• Recent Clips - The footage in Recent Clips continuously loops in 60-minute cycles whenever the cameras are activated. Therefore, footage is overwritten every hour unless you save it. When an event is recorded, one video is recorded for each of the front, rear, left, and right cameras.
• Saved Clips - Contains all recordings that you have manually saved using Dashcam.
• Sentry Clips - Contains the last 10 minutes of footage from all Sentry Mode events that have triggered an Alert or Alarm state. The footage from each event is labelled with a unique timestamp.
NOTE: As the USB flash drive runs out of available space, the oldest footage in Sentry Clips is deleted to make room for new footage. Once deleted, you are unable to retrieve them. When the flash drive is full, Sentry Mode and Dashcam can no longer save video footage. To prevent the flash drive from getting full, you must regularly move saved videos to another device, and delete them from the flash drive.
it gives you a warning message when its almost full and you have to manually delete it. this takes ages so i disconnect the drive and delete it on the computer. i think it overwrites old files but i rather just start clean.
As long as you don't fill the disk with DashCam recordings, the car will automatically delete the oldest Sentry Mode clips (this is a new-ish feature). Before, one had to manually clean up the USB stick every so often. Also, in the event you do run out of space, there is now a handy format button. Note, it will delete EVERYTHING from the stick, but it's a quick way to cleanup DashCam recordings.
I still have to delete everything on the USB in my wife's Model 3 from time to time. The car warns me when the USB is almost full. The USB in my wife's car is 64 GB. In my Model S I'm using a 128 GB microSD for video and it never seems to fill up.
I don't think it says this in the manual, but when the automatic deletion of SentryClips content was introduced, I think the release notes said it would only delete that content if SentryClips contains 5 GB or more of video. That shouldn't matter unless you're using a really small drive. The last time I had to clean up my wife's USB because the car said it was getting full, there was 54 GB in SentryClips.