There are several parts that make up a successful colocation data center, here are the five essential components:
Power is the most critical component of a data center facility, it's what powers the servers and data infrastructure. Typically power comes from a sub-station via two separate legs of power, is scrubbed to remove brownouts and is stepped down to 220V and 110V. Sometimes data centers will provide power straight from the power grid, which is much less reliable but quite inexpensive and suitable for data infrastructure housing archival and other types of low access data.
Data center providers have network carriers on-net and available for customers to negotiate with for bandwidth and connectivity solutions. Some data centers provide a blended BGP solution that combines on-net carriers for a fastest path bandwidth solution for customer. Additionally, colocation data center providers with more than one facility will likely have a network backbone that you can leverage for low latency failover from a primary site to a secondary site in another of their facilities.
All of the power that goes into the facility is converted to heat. That's a lot of heat to remove, and it's critical you remove it so that hardware operates at optimal temperature and humidity, otherwise equipment will fail and fires can occur. Some data center providers are able to bring in filtered air from the outside to cool the hardware efficiently, others have to cool the air before it gets sent to the hardware.
Security and Compliance
Data centers operate under closely monitored control procedures to ensure compliance with PCI, HIPAA and SSAE 16 requirements for data centers. All of these certifications are audited annually and consistently reviewed.
While the infrastructure and facility may be setup correctly it takes expert support and staff to operate it efficiently and effectively and without human error so as to preserve uptime. Data center facilities often promote from within those who show aptitude and discipline in providing expert support and customer service.