Data center architects naturally seek to employ server virtualization to maximize the use of their hardware systems. However, one factor – often overlooked – carries real potential to undermine this goal. That factor is data connectivity. This article examines the importance of data connectivity in a virtualized environment, and the need to take an intelligent approach to data access to truly reap the benefits of your virtualization strategy.

As strides have been made over the years in database optimization and the performance of processors and other hardware-based server components, the performance bottleneck has moved to the database middleware – the software drivers that provide connectivity between applications and databases. Between 75% to 95% of the response time now associated with database access can often be attributed to the data connectivity layer – and that’s using traditional non-virtualized servers. Running multiple virtual servers on a single machine can introduce additional complications involving data access.

Old Problems Become New Again
Exponential improvements in processor speed and design, continual strides in network capacity, and commoditized memory together promised to make hardware resource contention a thing of the past. However, with new capacity come new applications and new uses for information technology. In reality, the demand for applications is actually outstripping the ability of hardware improvements to accommodate them. That’s one reason why the number of x86 servers is projected to grow – according to IT research firm IDC – 39% by 2010 (adjusted down from an initially projected 61% due to the expected impact of server virtualization).

Consider this trend in light of the value proposition presented by virtualization technology: that you can use software to run multiple virtual machines (VMs) on the same single physical machine formerly employed as a dedicated server. Now multiple operating systems and their attendant applications must vie for the same discrete resources such as processor capacity, memory, storage I/O, and network I/O. The dormant issues of resource contention arise once again. Naturally, anyone considering a virtualized server environment must plan for sufficient hardware-based resource capacity to accommodate it. But adding additional capacity is not always feasible — flexibility in expanding network I/O, for instance, is something available only on relatively high-end machines.