In the last newsletter, we began discussing some of the challenges associated with server virtualization. In this newsletter, we will continue that discussion by talking about some of the specific WAN challenges that are associated with server virtualization.

Previously, we mentioned that when IT organizations implement server virtualization they often loose visibility to the traffic that goes between virtual machines (VM). The good news is that vendors are stepping up and offering products to meet that need. For example, Network Instruments recently announced that its Observer monitoring platform now provides complete visibility and in-depth analysis of application performance and traffic within both virtualized and physical environments.

According to Network Instruments, “Network teams using Observer can now access a complete, integrated view of virtual traffic traversing physical networks, between different virtual machine hosts, and between virtual machines on the same host. Further, all virtual traffic and communications flowing within the virtual machine host can be copied and sent to a GigaStor™ appliance for back-in-time analysis or the Observer Reporting Server for enterprise-wide performance reports.”

Relative to the impact of server virtualization on the WAN, the good news is that unto itself, server virtualization does not put additional traffic onto the enterprise WAN. However, many IT organizations implement server virtualization in conjunction with initiatives to remove servers from branch offices and place them into centralized data centers. 

Server consolidation does put additional traffic on the enterprise WAN and in some cases the amount of extra traffic can be significant. Further, the user now having access to applications over a WAN introduces additional latency, jitter and packet loss. In many instance those WAN impairments will not have a very significant impact on the performance of the application. However, as we have written before, if a chatty protocol such as Common Internet File System (CIFS) is running over the WAN, the typical result is unacceptable application performance unless the IT organization implements techniques to compensate for the chattiness.

In addition to these challenges, the combination of server consolidation and server virtualization creates an “all your eggs in one basket” situation whereby the corporate data center becomes even more critical to the business. This results in the need to increase the reliability of the enterprise WAN to ensure access to the corporate data center. We recently talked to the VP of architecture for a large financial services company. He explained that they used to have an availability goal for their WAN of five 9s. However, because they virtualized their data center servers, the new availability goal for their WAN is 100% availability.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.