Server Virtualization Growth: Slow but Steady

As most IT executives understand, server virtualization provides major opportunities to lower cost and improve productivity in the data center. Better utilization of computing resources lowers hardware cost, reduces floor space requirements, cuts power and cooling requirements, and improves IT staff productivity in deploying new OS instances. Combining virtualization with adoption of standard OS images (elimination of “one-off” OS configurations) yields even greater savings.

The latest metrics provided by our business partner Metrics Based Assessments LLC (MBA) shows these economic incentives continue to motivate IT organizations to increase their virtualization rates. At present, 95% of data centers are deploying some level of server virtualization, and the rate of virtualization continues to increase year by year.

As shown in Figure 1, the average number of Windows OS instances per physical server increased from 1.18 in 2006 to 1.35 in 2008, a 14% increase. On Unix platforms, the virtualization ratio increased from 1.16 to 1.37 in the same time period–an 18% increase. On Linux platforms, the ratio increased from 1.09 to 1.38–a 27% increase. Interestingly, the virtualization rate for these three platforms is now nearly the same.

Some data center managers may believe their virtualization rates are higher than the averages shown in Figure 1. Keep in mind, however, that the metrics shown in Figure 1 represent the average of all OS instances over all servers in the data center by platform. It includes servers running single instances as well as those that run multiple copies of the OS. In many data centers, a large percentage of physical servers are still dedicated to single applications–for example, production database servers. This causes the overall rate of virtualization to appear in the ranges shown in Figure 1.

Nevertheless, some data centers show much more aggressive use of virtualization. As shown in Figure 2, best-practice data centers achieve virtualization rates that are nearly twice the average rate. For Windows servers, the best practice data center is running 2.57 OS instances per physical server. For Unix and Linux, the best practice is approximately the same, at 2.46 and 2.52 respectively.

On individual servers, the number of OS copies can be even higher. Some benchmarking participants report successfully executing 10+ OS instances per physical machine.

These findings show that server virtualization has become the norm across all sizes and types of data centers. When viewed across the entire data center, the overall level of virtualization appears to be low–about 1.4 instances per server. But the rate has slowly and steadily increased over the past three years, and best practice organizations are achieving twice this level. In these times of economic recession, server virtualization remains a major strategy for cutting costs and improving resource utilization in the data center.

A complete set of data center benchmarks are available in Mark Levin’s book, Best Practices and Benchmarks in the Data Center.