The first part of this two-part article explained the importance of setting the right requirements as the start...
to designing a server room. This second part looks at the critical building systems to evaluate during server room design.
There is no single right way to approach server room design, but there are many best practices to follow, depending on the existing building and business plans
The major building systems to consider in server room design include physical space, mechanical systems, electrical systems and ancillary systems.
Finding the right spot
Locating your server room is an important first step and cannot take place in a vacuum. Consider your business needs.
Location. Take a server room's accessibility requirements into account when planning its location. IT teams move a lot of equipment in and out -- a distraction to nearby offices and a logistical challenge if the location is far from the loading dock or server-build area.
Easy exterior access makes for a less disruptive and less costly mechanical system and/or electrical system installation. However, exterior walls create thermal control issues. Ideally, choose a space with no windows, since windows are not as insulating as walls. Exterior walls and windows can also present a security risk.
Footprint. Will the server room need to grow in the future? If so, is the adjoining space "soft," such as offices or cubicle space that could be rearranged? Or is the server room abutting "hard" space, such as a cafeteria, elevator shafts, mechanical rooms or bathrooms? A good server room design best practice is to leave at least one direction for growth.
Structural load. The typical office-floor structural design may not be adequate to support the weight of loaded racks, mainframes or other equipment. Your server room design might change because of structural load -- spreading the load eats up a lot of extra space. You alternatively could add reinforcement above or below the floor slab. Slab on grade often provides a good foundation, but if the slab goes below grade level, there is a risk of flooding.
Water. Water and data center hardware don't mix. It's a best practice to keep the server room away from bathrooms or kitchens and their associated plumbing. If pipes are unavoidable, implement containment or drip pans in your design to shield hardware from pipe or roof leaks.
Interior design. No, it's not about lampshades and wallpaper borders. Your server room needs a ceiling, flooring and entrances. Here's a short list to review with the design professionals:
- Ceiling type: Hard ceiling, drop ceiling or no ceiling.
- Flooring: Static-dissipating tile, sealed concrete or another flooring material. If your design contact recommends carpet, beware. Also consider the effect of doing a raised floor before you start a server room build. Raised floors change your HVAC, electrical and cabling designs.
- Entrance: Vestibules or mantraps. A vestibule is almost a necessity if the space opens directly to the exterior.
Mechanical considerations in a server room design
Determine whether the building's mechanical system has the capacity or capability to support the server room. Consider the size of the building system and the economics of running it. The best practice is to have a dedicated air control system for the server room, separate from other spaces. You may use a standalone system for primary cooling, with the building system to supplement it during maintenance.
There are countless ways to design a server room's mechanical system: a chilled water system, a split system, an air-cooled system and so on. The right system depends on the server room's physical location, the budget and other factors. An exterior wall can allow an air-side, through-the-wall system. An interior server room could use a split system with rooftop or exterior condensing units. A building chilled-water system operating on the server room's schedule lends itself to use of chilled-water units.
An inefficient cooling strategy drives up operational costs. Segregating hot and cold air provides economic and performance benefits for the server room. Without air segregation, the warm return air mixes with the supply air, making it difficult -- if not impossible -- to provide enough supply air to cool hardware at higher densities.
Traditional air control involves a raised floor and cable routing that won't block airflow. With segregated supply and return air, raised floors are less important for air distribution.
Wiring up the data center
The electrical system depends on the specific server room's requirements and what's already in place.
All the server room's pumps, controls and other equipment need emergency power support. If you're implementing a standalone mechanical system, these loads will be easy to cover. However, if the mechanical system is supported by the building mechanical system, the electrical load could be too much. If the existing building emergency system does not have enough capacity to support the server room load, install a dedicated emergency power system.
Each way of handling power distribution to the end-use loads has advantages and disadvantages. Options include power distribution units spread throughout the space, remote power panels at each row and overhead busways. When there are multiple circuits to each device, such as dual-corded servers, a failure or a removal of part of the electrical system for service will redistribute the electrical loads, and could lead to a cascading failure.
The ancillary systems
The fire and life safety system interfaces with other building systems. For example, the HVAC system will shut down when smoke is detected. Since technology equipment can be damaged by a building sprinkler system, a dedicated subsystem for fire safety, with a dry-pipe pre-action system, is a smart design.
An emergency power off (EPO) system is sometimes required by the local authority having jurisdiction, or AHJ. However, EPO systems often cause many problems and inadvertent failures in a data center. If one is required, design a way to bypass it, and essentially deactivate it during maintenance activities. Always protect the EPO activation buttons against accidental activation.
Security can range from mantraps at the entrance to individual locks at each rack in the server room.
Test and test again
Every server room design project should include acceptance testing to verify that the loads are appropriate and failure is within set parameters. Without testing, even something as routine as a normal power failure could cause an unexpectedly long outage. Periodic retesting helps ensure proper operation of server room systems.
About the author:
Tom Langran is a licensed professional engineer with more than 15 years' experience in building design and construction. He has designed and managed data center projects for financial institutions and telecommunications carriers. He lives and works in Seattle.