We've tracked a trend for the past several years: customers aren't moving to standardize on a single brand or type of server, operating system, or even x86 hypervisor. But, in our in fifth annual x86 Data Center Survey (2011-‘12 edition), we were somewhat surprised to find that customers were using a wide range of different hypervisors to a greater extent than we anticipated.

The total number of respondents in our survey was 345, with 40% of respondents in mid-size and large organizations of 4,000 employees and above. This was a global survey; 46% of respondents hailed from Europe, 40% from North America, and 11% from Asia/Pacific. Respondents came from our Gabriel Consulting Group survey data base of previous participants and from targeted advertising.

Just over 80% of the IT shops in our survey are using VMware on at least some systems in their infrastructures. The company held roughly the same percentage of usage in both the 2009-'10 and 2011-'12 editions of our survey.

While VMware is the most prevalent, the company doesn't have a lock on the enterprise hypervisor market; other mechanisms are getting plenty of use as well.

Microsoft's Hyper-V product is the second most widely used hypervisor - around 40% of our enterprise data center respondents use it on at least some systems. This percentage has held roughly steady over both survey periods.

The major Xen variants from Citrix and Oracle are used by 32% and 21% of our survey respondents, respectively. These percentages are virtually the same in both our 2009-'10 survey and in our latest 2011-'12 edition.

The only virtualization mechanism showing growth overall is KVM, which moved from 31% to 33% prevalence in our two surveys. This clearly isn't a huge jump, but it's more than we've seen for other solutions.

Standardization of Hypervisor Platforms
Looking beyond which virtualization types are used, next we analyzed standardization on a particular hypervisor technology. We were able to trend this data as well. Again, VMware dominated but we detected more customers committing to KVM and Hyper-V as their "go-to" hypervisor technology. Let's review the numbers.

VMware has become slightly stronger in terms of being the standard virtualization solution for our enterprise data respondents, moving from 55% to 57%. But the magnitude of VMware's sizeable lead obscures the moves in the back of the pack.

We examined the same data, but with VMware removed to more clearly highlight the changes in standardization rate among the other hypervisors.

Customers standardizing on Oracle's version of Xen moved from 2% to 3% during the two survey periods. For Citrix Xen, we see a small drop from 4% to 3%. Both of these changes are probably due to differences in the survey respondent bases.

But when it comes to KVM and Microsoft's Hyper-V, we do think that we're seeing real growth. The number of customers who use Hyper-V as their standard solution more than doubled, moving from 3% to almost 8%. KVM also saw its customer standardization rates double from 3% to 6%.

Examining KVM's Growth
In fact, KVM is the only hypervisor in our last two surveys to notch gains in both the number of overall users and in the number of users adopting it as their standard go-to hypervisor.

These are modest gains to be sure, with overall usage increasing by 2% and standardizers growing from 3% to 6%.

While this isn't what we'd call "house on fire" growth, it's certainly a positive development for KVM and, given other KVM-related activities, might signal the beginning of a growth spurt.

We believe KVM capabilities have come a long way in the past several years, with support for a wide range of Linux, Windows, and even Unix guest operating systems. KVM also provides some of the most popular features of VMware and Xen, like live migration and the ability to host large (up to 16 CPU) SMP guest instances.

It's noteworthy that KVM is different from the others in a couple of crucial ways. It's the only hypervisor that's actually part of Linux and it uses the Linux scheduler and memory manager. Both VMware and Xen are external hypervisors and therefore need to have control mechanisms for the entire system, making them larger and more complex.

Summary
Despite VMware's big lead, competition in the hypervisor space is vigorous these days. Microsoft is using their heft to drive Hyper-V into their sizeable installed base. Commercial and open source Xen and KVM variants give customers alternatives that are technically sophisticated and also available as fully supported packages.

Our survey clearly shows that rather than selecting a single hypervisor and virtualization suite provider, customers are picking and choosing what they feel are the best tools for their unique needs. The more competition we have in this or any other market, the better the resulting products. Go here if you are interested in seeing more details on our report.