I was in a customer data centre today. It's quite impressive seeing all the racks of servers they have. The customer in question is one of the UK's leading banks and the physical security of the place is amazing:

• No company name on the building - you have to know it's the right place
• Double layer prison style fencing with security cameras
• Steel gate that opens for your car when buzz and speak to security
• You have to pass though an outer door (operated by security again) before signing in and picking up your pass
• To sign in you have to have a prearranged visit organised 72 hours in advance
• Then an inner door (security personnel operated)
• You are now in the building but only have access to the canteen and toilets
• You get collected by a member of staff and go to the data operations gallery to pickup a second pass (green level -> limited access)
• Finally with this second pass you get access to the room and rack where your servers are

Once inside the server room you understand the reason for all the security. It's full of mainframes and storage systems where the bank keeps their data. Very impressive to see and kind of makes our two 2U servers look a bit small.