What is a colo or Rackspace?
COLO (Colocation)
This is where you supply us with your own server and we supply the data centre and connection for it. So we provide a location to keep your server which is secure, has back up power, air conditioning and a fastreliable connection to the internet. Space is priced by the size of the server the smallest being around 1u (this is the height) and the largest being around 10u.

Rack Space
Very much the same as colo (above) but instead of one or two single servers, a certain amount of the complete rack* is leased. Either a half rack (minimum 22u) or a complete rack (minimum 44u) is available.

*In data centres servers are normally stored in tall metal racks which are normally around 19" wide by around 7' tall, this is know as 'rackspace'.