Data Center Security?
 

How should be security implemented in a datacenter? I wish to know not about the network security but the physical security aspects, like unauthorised access to the systems and likewise.

Just off the top of my head.

utilize a man trap for access.
24x7 NOC provides escort access to the DC floor. NOC holds cage or rack keys.
Cameras in the aisles without obstructions ie. doors.

Look for the DC to have a SAS 70 Type 2 certification and in most cases you will be pretty safe.

Yea, Authenticated access has to be made a must and Camerasof CCTVs are also a must. I do think using smart cards would eb a good idea.

Yes, I would recommend to have person 24X7 escort access which is more secure than other.