How to choose a modular data center

Modular data centers can be cost-effective, scalable options. There are several variables to consider, however, when comparing them to brick-and-mortar facilities.

By Debra Vieira, PE, LEED AP, ATD, CH2M, Portland, Ore. December 30, 2016

Learning objectives

  • Illustrate the various configurations of a modular data center.
  • Classify the advantages and disadvantages over traditional data centers.
  • Examine an example of a modular data center project. 

The lack of data center capacity, low efficiency, flexibility and scalability, time to market, and limited capital are some of the major issues today’s building owners and clients have to address with their data centers. Modular data centers (MDCs) are well-suited to address these issues. Owners are also looking for "plug-and-play" installations and are turning to MDCs for the solution. And why not? MDCs can be up and running in a very short time frame and with minimal investment-while also meeting corporate criteria for sustainability. They have been used successfully since 2009 (and earlier) by Internet giants, such as Microsoft and Google, and other institutions like Purdue University.

With that said, Microsoft has recently indicated the company is abandoning the use of their version of the MDC known as information technology pre-assembled components (IT-PACs) because they couldn’t expand the data center’s capacity fast enough. So which is it? Are MDCs the modern alternative to traditional brick-and-mortar data centers? This contradicting information may have some owners concerned and confused as they ask if MDCs are right for their building.

MDCs versus traditional data centers

There are many terms used to describe MDCs: containerized, self-contained, prefabricated, portable, mobile, skid, performance-optimized data center (POD), and many others. An MDC is a pre-engineered, factory-built and integrated, tested assembly that is mounted on a skid or in an enclosure with systems that are traditionally installed onsite by one or more contractors. An MDC uses standard components in a repeatable and scalable design, allowing for rapid deployment. A containerized data center incorporates the necessary power and/or cooling infrastructure, along with the information technology (IT) hardware, in a container that is built in accordance with the International Standards Organization (ISO) for shipping containers. A modular data center is not the same thing as a containerized data center; however, a containerized data center may be a component of a modular data center.

The IT capacity of an MDC can vary significantly. Networking MDCs are typically 50 kW or less, standalone MDCs with power, mechanical, and IT systems can range up to 750 kW, and blade-packed PODs connected to redundant utilities may be 1 MW or greater.

There is a lot of disagreement in the data center industry in regards to the performance, cost-effectiveness, time efficiency, and standardization of MDCs, and their ability to outperform traditional brick-and-mortar data centers that use a standard, repeatable, and scalable design. An advantage of an MDC is its ability to be shipped anywhere. It can arrive as a single, stand-alone enclosed unit, be integrated into an existing data center, or be combined into a system of modules to establish a large-capacity data center.

According to 451 Research, the MDC market is expected to reach $4 billion by 2018, up from $1.5 billion in 2014. In addition, 451 Research believes that MDCs are strategically important to the data center industry. MDCs are expected to play a significant role in the next generation of products and technology, as they offer a flexible data infrastructure that can be built in larger "chunks" than many scalable brick-and-mortar data centers. MDC designs are improving, and owners and operators are becoming better educated about the many available options and variations. Due to the growing interest with MDCs, there has been a surge in suppliers. An Internet search for MDCs yields more than 20 different organizations with varying types of products-and this list is expected to grow as vendors use technology, innovation, and geography to gain a competitive edge. MDCs can be purchased or leased in many different configurations, such as:

  • Only equipped with IT hardware
  • Power and/or cooling with space for IT hardware
  • Power and/or cooling and equipped with IT hardware
  • Only equipped with power or cooling.

Leasing options offer significant flexibility in the physical location of the MDC. Some lease options allow the MDC to reside onsite, or the MDC infrastructure can be leased from a co-location provider who is delivering services. Comparing MDCs and available options can quickly become overwhelming. There are containerized, pre-engineered, and prefabricated versions. IT vendors have MDC products that are complete data center solutions and are engineered to work specifically with their hardware, but they typically work with IT products from multiple vendors. Some providers deliver co-location and cloud services using MDC technology.

MDCs can reduce capital investment, construction, and schedule, provide for faster deployment, and offer flexibility for changing IT technologies. MDCs also reduce the risk associated with design, such as the technical risk of the design not adhering to the requirements, the schedule risk of the design not being completed on time, and the cost risk of the final product exceeding the budget. Providers of MDCs offer turnkey solutions for customers who do not have the in-house skill set to design and construct their own data center. Here is a look at a few more key advantages of MDCs:

  • Improved schedule: MDCs are standardized, allowing for fast construction and module commissioning within a few months (or less). They are manufactured offsite and transported to the construction site for final placement and utility connection. This allows for site preparation to occur at the same time as MDC construction, rather than the traditional linear process of site preparation before construction of the data center. When evaluating traditional construction versus MDC, consider the speed needed to deploy and whether the deployment is required at one or multiple sites. The increased quantity of data center sites results in a more complex deployment, which may be eased by using MDCs.
  • Reduced capital investment and risk: Brick-and-mortar-type data centers are expensive to build and involve significant risk (i.e., going over budget, missing schedules, not meeting requirements). Both MDCs and traditional data centers can be sized to known criteria with the ability to easily expand, however, MDCs allow the provisioning of "just-in-time" data center capacity by matching the investment to the planned growth. The risk associated with the manufacturing of the MDC lies with the manufacturer who is accountable for the cost, schedule, and performance of the MDC. Whereas in a traditional brick-and-mortar data center, the risk associated with construction, cost, and performance is the owner’s responsibility.
  • Flexibility and scalability: With the ability to provide a quick response comes the agility to scale data center capacity to actual business needs rather than trying to predict capacity years in advance. MDCs allow power, cooling, and IT capacity to be deployed when required. Through the use of MDCs, changes in densities, space requirements, or IT technologies can be easily incorporated rather than retrofitting a more traditional facility that was constructed years ago to old requirements. MDCs can be prefabricated, allowing the use of an industrialized approach for standardization in the design, construction, and operation of the modules. In fact, operation of multiple modules can be identical. While this approach can also be used for traditional data centers, the speed at which MDCs can be deployed may be an advantage.
  • Performance, efficiency, and power-usage effectiveness (PUE): MDCs are very efficient and can accommodate densities as high as 20 kW per rack and potentially higher. However, the cost savings associated with higher-density racks diminishes quickly around 5kW per rack, with no savings realized beyond 11 kW per rack. Cooling systems are optimized for local site conditions along with the internal IT systems. The PUE metric is a good measure of efficiency for MDCs, but a word of caution: Many MDCs require external power and cooling connections, therefore, the represented PUE may actually be a partial PUE (pPUE). When evaluating MDC products, verify that power and cooling requirements are properly represented and compared with each product by working with the vendor to determine what they have included and excluded in their PUE number.
  • Prefabrication: The risk associated with the manufacturing of the MDC lies not with the owner, but with the manufacturer who is accountable for the cost and performance of the MDC.
  • Flexible site selection: Is the intent of the MDC to be mobile or will it remain in one location? MDCs can be disassembled and transported to another site for quick assembly to provide for contingency operations during a natural disaster or for temporary cloud computing, similar to the needs of the U.S. Army. In some cases, the availability of materials and the logistics of building a data center in a remote location makes the MDC a good solution, like in the oil and gas industry.
  • Disaster recovery: Is disaster recovery a major consideration for your company? Even if a company does have a disaster recovery center, is it capable of handling the failure for an extended period of time, such as in the event of a major hurricane or flooding? An MDC may be an effective strategy for disaster recovery since it can be quickly deployed to a site.


With all the benefits of an MDC, it’s easy to forget about some of the negatives, such as depending too heavily on the design of the MDC for high availability. The MDC will be operated and maintained by workers, which makes it difficult to eliminate human error. Security of an MDC is also a significant issue. For example, with the opening of just one door, you are in the heart of the data center. Also, a bullet can penetrate the shell or a vehicle can ram into the MDC. Some of the security issues can be addressed with bollards or berms around the MDC. Containerized data centers are in an ISO box, which is not aesthetically pleasing and may not be allowed in some business parks without additional screening and landscaping. Many MDCs have a single utility-connection point for power and cooling, which can be a point of failure for the MDC. Once built, an MDC is difficult to modify and may require specialized support. Maintenance of the MDC may also be difficult during inclement weather since entry doors are limited and access panels often expose critical systems to the weather.

Site preparation is an important aspect of MDC installation. This includes the need for civil, mechanical, electrical, and telecommunication site plans that focus on the slabs and foundations as well as the utility and networking interconnections to the MDC units. Additional design considerations should be given to MDCs located in seismic regions for proper anchoring and isolation. These types of issues should be considered when evaluating an MDC solution.

Regardless of the type of data center construction (brick-and-mortar or MDC) the purchase or lease price of the property, site development costs, and the impact of local environmental conditions on the energy required for cooling need to be considered in the site-selection process. Site location can impact labor costs. If the data center is built in a location that has low labor costs, then the cost savings of a premanufactured data center may not be realized. Whereas if the labor costs are high, then the use of MDCs may offer a cost advantage.

The process of reviewing and approving site plans may be improved by an MDC, which is certified by Underwriters Laboratories (UL) and/or Conformité Européene (CE). This allows the permitting agency to focus only on the installation of the MDC, rather than the internal subsystems of the MDC. UL 2755-Modular Data Center Certification Scope and Process addresses issues, such as:

  • Potential enclosure hazards
  • Transportation hazards
  • Electrical construction
  • Supply and distribution
  • Working-space exit routes and signage
  • Fire detection and suppression
  • HVAC
  • Installed equipment
  • Noise exposure.

Since the MDC may be supplied through existing on-premise wiring systems or through a separate MDC enclosure, the data, fire alarm, communications, control, and audio/video circuits from the MDC are typically brought into an existing facility. If the MDC is UL-certified, then the evaluation of the equipment, installed wiring, lighting, and work space is conducted as part of the listing; only field-installed wiring is required to be reviewed and comply with NFPA 70. Nonlisted MDCs may also be installed under Article 646 of the 2014 edition of the NEC; however, all components must then be installed in accordance with the code.

For additional information on the design, efficiency, procurement, and installation of MDCs, Lawrence Berkeley National Laboratory, on behalf of the General Services Administration, prepared a vendor-neutral MDC procurement guide. Furthermore, the Data Center Knowledge Guide to Modular Data Centers provides substantial information on different MDC solutions and highlights many practical considerations when purchasing an MDC.

Choosing between MDCs and traditional data center construction is not a simple decision. There are some issues where an MDC may not be the right solution or will require special construction techniques to mitigate, such as security, maintenance during inclement weather, and the need for redundant utility connections. However, MDCs can offer multiple advantages that may be crucial to a business’s strategies and growth. With their lower initial investment and faster deployment, scalability, and flexibility, MDCs should be considered as a possible solution. MDCs are highly efficient and offer many of the same options that are available through traditional data center construction. MDCs can be implemented as a turnkey solution, thereby reducing risk and making them an attractive choice. 

Debra Vieira is a senior electrical engineer at CH2M. She specializes in data center and mission critical environments.