Applies to: Reolink NVRs 

You could refer to the articles below to set the HDD to overwrite old files.

How to Set the HDD to Overwrite via Reolink App

How to Check/Format HDD via Reolink Client (New Client)

How to Set the HDD to Overwrite via Web Browsers

How to Set the HDD to Overwrite via Reolink PoE NVRs

How to Set the HDD to Overwrite via Reolink WiFi NVRs