aarondsouza, hope this is of some use to you
Fires are grouped in to five different classes.
Class A fire - is for flammable solids, like wood, waste paper and fabrics and some plastics.
Class B fire - is for liquids, like solvents, petrol kerosene, and some oils.
Class C fire - is for flammable gases, like butane, propane and natural gas.
Class D fire - is for metals such as aluminium, magnesium, titanium
Class F fire - is a special class of fire specifically for oil in deep fat fryers.
Note: For Class C and D fires, specialist advice should be sought.
Portable CO2 as you ask is particularly suitable for dealing with small fires involving electrical equipment, and can also be used on Class B fires,remember once the source of the electricity is shut down, the electrical fire will revert to a different class.
For your server room the one to have on standby would be a CO2