HIKVISION HWN-2104H-4P User Manual page 186

Set the HDD property to R/W, Read-only or Redundancy.
Click the OK button to save the settings and exit the interface.
In the HDD Information menu, the HDD property will be displayed in the list.
At least 2 hard disks must be installed on your NVR when you want to set a HDD to Redundancy,
and there is one HDD with R/W property.
Network Video Recorder User Manual
Set HDD Property
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