The easiest way to do it is to use a NAS that supports direct camera
recording, and cameras that it specifically supports. We use QNAP NAS
arrays regularly, they support several IP cams in addition to other
standard NAS functions. QNAP also makes dedicated NAS units.
Network path is not required - you simply tell the NAS the address of
the supported camera(s) and it operates as an NVR.
For remote recording, you could use a NAS the same way, connecting to
the camera via VPN.