SDN as a Catalyst for Change in Data Center Design

Software defined networking, or SDN, is the buzz term in the industry, and rightly so. By introducing programmability into networking, SDN has the potential to fundamentally change the way networks are built, provisioned, and managed.

Within the data center, SDN's benefits are even more profound. Virtualization is now putting intense pressure on the data center network.
Instead of a single physical server with a single network connection, we can now have 10, 20, and even much higher numbers of virtual machines (VMs) running inside each physical server, each with its own network requirements. Adding to that complexity is the emergence of cloud, which enables automated provisioning of VMs, creating a much more dynamic environment.

Without SDN, every time a virtual machine is brought up, moved, or decommissioned, someone has to manually reconfigure the network. With SDN, network administrators handle network changes via a software interface. Instead of taking hours, or days, to set up a network connection, SDN can do it in minutes. Given the right software and solution, the network can even reconfigure itself.

Take that one level higher into the realm of multi-tenant carrier neutral data centers running cloud platforms, and the benefits of SDN multiply exponentially. But while SDN will definitely revolutionize the data center network, it also has significant impacts on the physical data center.

A MORE DYNAMIC DATA CENTER

For carrier neutral, multi-tenant facilities like Pacnet's data centers, there are obvious challenges when customers can start to dynamically shift their server loads between different parts of a facility, and even between different facilities in different regions.
In the past, the formula for filling out a facility was relatively simple. As new tenants move in, we can estimate how much power they will need to run their servers, how much heat those servers will generate, and where those servers are located. We then deliver our UPS and cooling capacities to match.

But when customers can reroute their server loads between racks, or between actual data centers, that formula goes out the window since we can't predict where our customers will be running their compute cycles. This means that we have to be able to handle much more dynamic loads, particularly from a thermal management perspective. First and foremost, we need to build more dynamic cooling.

We not only need to build cooling capacity for peak load, but must also be able to scale that down as loads subside, to maximize the full benefit of the virtualized data center. In this way, the SDN-enabled data center must be capable of the same flexibility that the data center network now possesses.

At Pacnet, that means a modular cooling infrastructure that allows us to turn on and off capacity rapidly to match the load of our customers. Through a combination of large and small chillers, we can regulate our cooling capacity. The large chillers are like marathon runners that take care of the basic load, while the smaller chillers behave like sprinters, designed to run during periods of peak load.

THE ELEGANT FACILITY

Besides making the data center a more dynamic environment, SDN also enables a range of next generation innovations. SDN liberates the network from the physical cables. The physical cables themselves no longer dictate the path of the connection, since SDN allows for the dynamic configuration-and reconfiguration-of networks. The physical cables become a single unified platform, one that can be pre-installed, optimized like the electrical cabling.

The result is a cleaner, more elegant data center environment. Less cable ducts mean better airflow, leading to better thermal management. In fact, we are doing just that within a new facility we are building. More importantly, we are not only changing the way the passive cabling ducts are designed, we are changing the cables themselves, increasingly moving from traditional CAT5/6/7 cables to fiber, further reducing the footprint of the cabling while ensuring scalability to support the most demanding loads.

What we offer customer is akin to a ‘network on a plug', much like we offer power from an electricity outlet. We can do that now because the physical cabling no longer restricts how the network is configured. With SDN, the network is virtualized, programmable, and boundless.

TOWARDS A NEXT GENERATION DATA CENTER

At the end of the day, SDN can go a long way in advancing how corporate IT systems are built and managed within data centers-even between data centers. It unifies corporate compute resources under a single domain regardless of location, and offers unprecedented flexibility in how to deploy those resources.

In so doing, SDN presents some obvious challenges for data center facility managers. Keeping up with that level of agility will require a rethink of how facilities are designed and built. But if we manage to get it right, we get to take the data center to a whole new level of efficiency and agility.

Looking ahead, a fully SDN-enabled data center networking environment can do much more for multi-tenant, carrier-neutral facilities. Instead of enterprise customers connecting to each external network provider over a cross-connect, everyone can link into a common network fabric.
With SDN, network paths and capacity can then be allocated dynamically to whoever needs that connection. The possibilities are limitless for new ways for delivering services, new applications, new business models.