Data Center Support Systems

A data center must provide certain services:

• Locations on the floor that can support the weight of the racks

• Power to run the racks

• Cooling to keep the racks from overheating

• Connectivity to make the devices in the racks available to users

• Planned redundancies

If any one of these services fail, the system will not run effectively, or at all. These support systems are how a data center supplies its intended services. They are also interdependent. If you can't place the server in the data center, it won't run. If you can't get enough power to run the server, it won't run. If you can't cool the server, it won't run for long, a few minutes at best. If you can't connect the server to the people who need to use it, what good is it? All of these requirements must be met simultaneously . If one of them fails, they all might as well fail. Your data center can only be as effective as its weakest support system.

Space and Weight

You have to be able to place the servers in the data center and, depending on the type of server, you might need even more space than its physical footprint to cool it. This is the cooling footprint. Weight is also a major consideration. If you have space for the machine, but your raised floor can't handle the weight load, it will crash through the raised floor. The ramps or lift you use to get the machine onto the raised floor must also be able to handle the weight load of the system.

Power Requirements

It is essential that the data center be supplied with a reliable and redundant source of power. If computers are subjected to frequent power interruptions and fluctuations, the components will experience a higher failure rate than they would with stable power sources. To assure that power is up constantly, multiple utility feeds, preferably from different substations or power utility grids, should be used. Also, the data center should have dedicated power distribution panels. Isolating the data center power from other power in the building protects the data center and avoids power risks outside your control.

The power distribution system is covered in more detail in Chapter 7, "Power Distribution."

HVAC and Air Flow Requirements

Placement of the HVAC (air conditioning) units is highly dependent on the size and shape of the data center room, as well as the availability of connections to support systems. The primary concern in placement is for optimal effectiveness in dealing with the planned load.

Air flow must be considered in the layout of the HVAC systems as well. Reducing obstructions under the floor will provide the best air flow to the areas where the air is needed. Air flow is also governed by under-floor pressure, so the placement and distribution of solid and perforated tiles on the raised floor should be carefully considered. You must maintain higher air pressure under the floor than in the data center space above the floor.

Air conditioning and HVAC placement is covered in more detail in Chapter 8, "HVAC and Other Environmental Controls."

Network Cabling

Network cabling is essential to a data center. It must supply not only TCP/IP connectivity, but connectivity to Storage Area Networks (SAN) as well. Storage systems are becoming increasingly "network aware" devices. Whether this has to do with managing storage through TCP/IP networks or with using these devices on SANs, the requirements of the network cabling must be flexible and scalable.

Most of these requirements can be met using Cat5 copper and multi-mode fibre. However, some single-mode fibre might also be needed to support WAN requirements. Understanding what equipment will go where and knowing the cabling requirements of each piece of equipment is integral to building data centers. Of all of these support systems, upgrading or adding more network cabling inside the data center is the least intrusive support system upgrade.

Network cabling is covered in more detail in Chapter 9, "Network Cabling Infrastructure."

Planned Redundancies

It is important to consider all of the possible resources that will be needed for redundancy. Particularly, consider redundancy for power and environmental support equipment. Redundant systems allow for uninterrupted operation of the center during electrical and HVAC upgrades or replacements . A new HVAC unit can be run simultaneously with the hardware it is replacing rather than swapping the two. Redundancy assures that power and environmental controls are available in the event of power or equipment failures.

Plan for at least the minimal amount of redundancy, but also plan for future redundancy based on projected growth and changes within the center. Will the focus of the center change from a development to a mission critical facility? Will redundant HVAC units be necessary and, if so, where will they be placed? Should greater capacity electrical wiring be pre-installed for future systems?

It is important that the intentions for redundancy be maintained as the demands of the data center change and grow. Extra floor space or support systems that were planned for redundancy should not necessarily be used for expansion if this strategy means increasing the chances of downtime due to failures. Make sure the blueprints clearly indicate the intended purpose of the space and systems.

The biggest problem with allocating less redundancy to create more capacity is in the area of sub-panel and circuit breaker space. You should allocate space for at least one additional sub-panel and breakers in the mechanical room for each megawatt of power you have in the data center.

Also, consider redundancy for UPS and emergency power generators. While these are large expenditures and twice as large if they are totally redundant, in a mission critical data center where the cost of even one minute of downtime can cost millions of dollars, they could be a prudent investment. Use the resources of your risk analysts to determine the cost-effectiveness of these redundant systems.