The DVR can add a hard drive to store data from an analog camera attached to the DVR. Note: The DVR is connected to an analog camera.
The NVR is more like a disk array and provides network storage space for IPCs or DVSs. That is, the NVR stores code streams that are encoded and transmitted over the network. The NVR is connected to a network camera.
Specifically, you still have to choose between them, please check this topic
https://forum.huawei.com/enterprise/en/what-is-the-difference-between-the-nvr-and-dvr/thread/716303-887