Engineering notes
An NVR is not a PoE switch: ports, watts, retention
A 16-channel PoE NVR is enough for a small job. 24 cameras, night IR, 30-day retain — split the PoE switch and the disks.
The schedule has one line: “16CH PoE NVR”. Fine for ten indoor heads and a short retain. Twenty-four gate cameras at night, thirty days — the NVR’s PoE budget dies when IR turns on, the internal disks fill in week three. That is not “a bad camera”.
NVR: channels, codec, bays, RAID if the file asks. Switch: watt total, port count, uplink to the recorder — its own lines. Do not take an 8-port PoE NVR and daisy-chain a cheap switch with no budget. Days × bitrate × channels, plus about 20%.