For server room use "FM 200 ,, HFC-227ea" or "Novec"
Use
NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems

or my favoure
8.5 % by volume , by ISO 14520-9 / EN 15004-5

or even VdS 2380en
Fire Extinguishing Systems using non-liquefied Inert Gases, Planning and Installation

regards,
zaconja