Bringing Clarity to Modular Data Center Architectures

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Anyone who pays even scant attention to data center issues has no doubt been hearing the term “modular” with increasingly greater frequency, and with good reason. As we’ve covered previously, modular data centers bring many benefits, including cost savings up front and over time, increased reliability, improved efficiency and more.

But the definition of modularity remains vague, and presents data center operators with a confusing number of poorly defined terms like pods, containers, clusters, zones, rows, rooms and more. To help bring some clarity to the issue, Schneider Electric’s Energy University offers the course, “Modular Data Center Architecture I.” The course creates a framework for understanding modular data center architecture concepts and terms, and describes the various ways it can be employed for data center power, cooling and space infrastructure.

As the course explains, modularity is loosely defined as a technique that builds large systems out of smaller subsystems, with well-defined rules for connecting them to one another. Modularity also suggests a simplified approach to installation or replacement, ideally with “plug in” modular elements that make for simplified commissioning.

The course defines three types of modularity with respect to data center architecture:

• Device modularity: devices that are made up of modular components
• Subsystem modularity: a functional block made up of multiple devices or modules of the same type
• Module linkage: relationships between modules of different subsystems, determining how redundancies, capacities, and densities are achieved and scaled over time

IT equipment has long seen a trend toward device modularity with respect to servers, storage devices, networking equipment and more. But now the modularity trend is extending to data center infrastructure, for systems such as computer room air conditioning (CRAC) systems and power distribution systems.

The benefits of device modularity include serviceability, provisioning speed, capacity changes, acquisition lead time and the ability to more easily reconfigure systems. As the course makes clear, however, the use of modular devices by itself does not mean a data center has a modular architecture.

The next step up, subsystem modularity, involves linking multiple devices into a single functional unit. Subsystem modularity is ubiquitous in larger data centers where subsystems like PDUs and CRAC units are almost always comprised of multiple units. And it doesn’t necessarily matter whether the individual components of a subsystem are modular devices; so long as a subsystem comprises multiple devices working as one, it is considered modular.

Subsystem modularity delivers greater fault tolerance, to the extent the subsystem can survive the failure of one of the modules while still handling its load. Maintenance is also simplified when a module can be taken offline for testing or maintenance without disrupting the load. Subsystem modularity also simplifies logistics when modules are small enough to be moved via passenger elevators and through doorways.

Here again, however, using modular subsystems does not necessarily mean you have a modular data center. For that, the design must specify how the different subsystems are deployed together.

That gets into the third criteria for a modular data center: module linkage. A modular data center architecture must have some approach to group the subsystems so they can be deployed in a logical and coherent way. Module linkage defines how the different subsystems relate to each other.

Consider the deployment of equipment racks and rack power strips. In this simple case you may define a 1:1 deployment, one rack for every rack power strip. Now consider the deployment of PDUs and racks, where you might define a rule linking one PDU to every 20 racks. Then maybe it’s one generator for every 500 racks, one CRAC for every 40 racks, and so on. The rules relating these deployments are “linkages” of the modularity of the different subsystems. These linkages may be as simple as rules of deployment, or they can be enforced by pre-engineered and pre-manufactured skids, containers or “kits” of deployment.

That is just a taste of what you’ll learn in the hour-long course, “Modular Data Center Architecture I.” You’ll also learn about the effective attributes of a modular data center architecture and the importance of using standardized architecture. You’ll find the course in the College of Data Centers on the Energy University site.