Making server closet. Curious of how to add good airflow.
Also, should I put a full door cutting the piece of drywall out, or keep it half way? I was thinking full door so I can get side/rear access. Any tips please!
Disregard vents. Acquire open loop falling film radiators, exhaust directly outside.
Like you say, put a full door in for ease of maintenance and access, you're better doing it now than realizing what a PITA it is and getting drywall dust all over your server vents if you decide to do it later.
You can buy doors with pre-installed louvers (pic related), or you could make your own, but make sure it has fine dust filters to filter out as much dust as possible, dust = bad.
Inside you want each server rack with a fan for circulation if possible PLUS a main air conditioning system as circulating hot air only does so much. Ideally you want the temps to be in the mid twenties (Celsius).
Remember, warm air rises, cold air sinks, so situate any circulating fans as such (cool air INTAKES at the bottom, hot air EXHAUSTS at the top). Make sure you site your fans so they don't fight with eachother (e.g. an intake fan 10mm below an exhaust will just mean a circle of air in and out in that very small area).
Make sure there's nothing in the closet or passing through like hot water pipes, hot HVAC ducts etc. as this will just add to the heat load dramatically. Similarly, any water pipes above the server rack should be bunded so if it leaks it won't fuck your server up.
That any help?
Also OP, make sure you have some good cable management in there. Two reasons, a shit ton of 230VAC (or whatever your mains voltage is) cables twisted around eachother or looped in a pile will get hot or potentially overheat (if it's really bad).
Also, cable nests seriously restrict airflow.
If possible, use either conduit, cable tray or trunking and really make sure it's neat as fuck. Alternatively, use a powerbar system, basically a bus bar within the server enclosure which you just connect up to your server racks with like 30cm of cable, rather than shitloads of trailing cables.