We’ve talked about why the right network for a private cloud needs to be lossless, resilient, and converged. It also needs to be edge-configurable and software defined. Let’s take a look at these attributes.
Edge-configurable. Applications run at the edge of the cloud network, but legacy networks are typically administered from the center. This is great for the job security of network engineers but not so helpful for handling the kinds of automatic network changes that occur in clouds. For instance, if a service level agreement (SLA) calls for moving some virtual machines (VMs) around to improve performance to meet customer objectives, waiting on a network engineer to reconfigure the network for the moved workloads is both inconvenient and an opportunity for outage-inducing human error. You want a network that can take operational orders from edge servers, and ideally, from individual hypervisors. A hypervisor should be able to say "move this VLAN from host 5 in chassis 3 to host 12 in chassis 29." That's edge-configurability in a nutshell. Be sure to get this feature in your network. An important standard on this front is Edge Virtual Bridging (EVB), which Microsoft supports in Hyper-v 3.0.
Software-defined. You've probably been hearing a lot of buzz about Software Defined Networks (SDN). Some technologists think that SDN is the technology of the future. But SDN is here today, in the form of centralized orchestration of cloud services. SDN is a realm in which hardware and software vendors work together to make the whole network greater than the sum of its parts. For example, HP's IRF-capable 5900AF physical switch has a virtual edition, the 5900v virtual switch, which can dovetail with management and networking components within a hypervisor to let an orchestration system, such as Microsoft System Center, configure both hardware and software to meet the networking needs of tenant workloads.
So shop smart when you shop networks. Make sure that you use vendors that hit the minimum marks with their products, and don't be afraid to ask for demonstrations of promised capabilities. You'll then be well positioned to buy a virtual network that is truly cloud capable.
After you've specified the servers and networking of your private cloud, you're halfway home. In our next installments, we'll examine the speeds and feeds of virtualized storage components for your nascent cloud.