Thinking Outside of the Rack: Designing and Planning by Pod

28 June, 2017
Patrick Donovan
Schneider Electric

IT PodIn olden times, the supporting infrastructure for data centers and IT rooms would be built out all at once…based on some vague understanding (guess?) of what future IT needs would be 5 or more years down the road. This obviously led to overbuilt and/or stranded capacity as one resource got used up before others.  Some of this behavior was driven by budgeting practices, perhaps…“this is my one shot, so I’m going to try to get as much as I can possibly get”-type of mentality. But as modular power and cooling systems and architectures began to emerge, building in more of a “pay-as-you-go” approach came into being.  The IT rack rather than a server became the core unit of organization that designers use to estimate the requirements of the facility.  Knowing average and peak rack power densities along with the number of racks not only allows for efficient facility sizing, but also determines branch circuit ratings and the heat rejection needed for each rack.  Racks have typically been the unit of deployment in data centers.  They mark the location of physical servers and their VMs. In DCIM systems, dependencies on power paths and cooling resources are mapped to the rack.

However, for larger data centers, IT deployments often come in larger and larger chunk sizes.  These “pods” of racks are deployed together and typically share common resources such as air containment systems, a PDU, network switch, or perhaps are grouped because they share a business function or serve a particular client or tenant.  But unlike the simple, highly standardized 19” rack, there is no industry standard for IT pod design and deployment.  White Paper 260, “Specifying Data Center IT Pod Architectures” proposes a high level standardized spec (see below) that can be used to define IT pod requirements and help to compare and contrast design alternatives quickly.

high level standardized spec for Data Center IT Pod Architectures

When you consider typical voltage levels and commonly available breaker sizes, a low and high power pod emerge as logical architectures to standardize on.

 low and high power pod architectures chart

When viewed in the context of different average rack power densities, you start to get a sense of the pod size:

different average rack power densities chart

The paper explains these 3 main drivers of an IT Pod’s design in detail: the choice of the electrical feed (power), the physical space available (i.e., number of racks), and the average rack power density required.  When commonly available voltages and breaker sizes are considered, optimum pod configurations emerge that make planning and design easier.  Standardizing pod designs and limiting the number of configurations, as shown in the paper, can help make pod-level deployments simpler and faster.  Organizing IT racks into pods makes it easier to vary power and cooling redundancies and architectures based on the specific business needs within an IT room or hall.  A free-standing pod frame system can decrease data center project time by reducing construction time, allowing off-site integration of IT racks and IT gear.  In addition, it simplifies maintenance by making it easier to roll racks in and out since containment and services are mounted to the frame instead of the rack.  Using the pod specification table shown here can help project teams clearly specify and repeat designs for current and future projects.

To help make specifying the design of the white space even easier, we created an IT Pod Sizing Calculator that is free and simple to use…check it out!

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