How much bandwidth does a data center really need? It depends on how many workloads and virtual machines are in regular operation, as well as what the facility is designed to support. For example, a data center providing resources to a public cloud requires much more bandwidth than one that is simply powering internal systems and operations shielded by the company firewall. The increasing uptake of remote data centers and colocation arrangements, in tandem with server virtualization, has added to organizations' bandwidth considerations.

How virtualization complicates bandwidth requirements
Server and desktop virtualization have made companies less reliant on physical infrastructure and the specific sites that house it. Here's how they work:

  • With desktop virtualization, or VDI, an operating system can be hosted by a single machine (even an aging one), simplifying management of both software and hardware while reducing costs
  • Server virtualization involves a single physical server being turned into multiple virtual devices. Each instance is isolated and the end user cannot usually see the technical details of the underlying infrastructure.

By getting more out of IT assets via virtualization, companies have reshaped IT operations. More specifically, they have spread out their infrastructure across multiple sites and put themselves in position to move toward cloud computing.

With increased reliance on virtualization, organizations have looked to ensure that remote facilities receive the bandwidth needed to provide software, instances and data to users. However, liabilities still go overlooked, jeopardizing reliability – especially when data centers are too far apart from each other.

Ensuring low latency is just one piece of the data center optimization puzzle, though. Sufficient bandwidth must also be supplied to support the organization's particular workloads. In the past, Microsoft has advised Exchange users to think beyond round trip latency.

"[R]ound trip latency requirements may not be the most stringent network bandwidth and latency requirement for a multi-data center configuration," advised Microsoft's Exchange Server 2013 documentation. "You must evaluate the total network load, which includes client access, Active Directory, transport, continuous replication and other application traffic, to determine the necessary network requirements for your environment."

Knowing how much bandwidth is needed
Figuring out bandwidth requirements is a unique exercise for each enterprise. In a blog post, data center networking expert Ivan Pepelnjak looked at the nitty-gritty of assessing bandwidth-related needs, honing in on some of the problems that reveal a need to rethink how bandwidth is allocated and utilized.
These issues include:

  • Over-reliance on slow legacy equipment
  • Oversubscription to services
  • Miscalculation of how much traffic each virtual machine generates 

In addition, data center operators sometimes overlook bottlenecks such as how virtual machines can sometimes interact slowly with storage. If they have to frequently access data stored on an HDD, for example, quality of service may degrade. Networks may require extra bandwidth in order to avoid data transfer hiccups.