VMware is making a free benchmarking tool available to IT professionals Monday to evaluate the performance of virtualization technology in their datacenters. Meanwhile, it seeks to assure competitors that the benchmarking standards will be fair to all of them.

VMmark is available for a free download and can be used to determine how well virtualization software works with any of six typical datacenter workloads: file server, e-mail server, Web server, a standby server, an online transaction processing (OLTP) database, and a Java order entry system. VMmark runs on either Linux or Windows.

VMware shared a prototype of VMmark in October 2006 with members of the Standard Performance Evaluation Corp. (SPEC), an industry group that establishes performance benchmarks so customers can evaluate products. At that time, SPEC had just formed a working group to develop benchmarks for virtualization software. It is still working on those benchmarks.

Though helpful for comparing various products, benchmarks are controversial because of concerns that the results can be manipulated to make one vendor look better than another. SPEC and other industry benchmarking groups are organized to create fair benchmarks that will yield impartial results.

VMware acknowledges the skepticism about its benchmarking tool being a fair way to compare VMware with other brands, so it strove to be impartial, said Andrea Eubanks, senior director of enterprise and technical marketing for VMware.

VMware is represented on the 13-member SPEC work group that is developing the virtualization benchmark along with competitors such as SWsoft and Trigence. Major technology companies including Hewlett-Packard, Microsoft, and Intel are also represented.

"We have created VMmark to be an open standard," said Eubanks. "In order to prevent misconceptions of what our intentions are. ... we presented our technology preview to SPEC so they could use it as the basis of the open-standards benchmark. We want to improve our product, we don't want to cook our benchmarks."

VMware is introducing VMmark while the SPEC panel is still developing its standards. "The process to becoming a standard is a quite long one," said Eubanks.

But VMware has not always been as impartial as it claims to be, said John Bara, vice president of marketing for XenSource, a VMware competitor.

Bara says VMware released a white paper earlier this year comparing VMware's ESX Server hypervisor to XenSource's Open Source Xen hypervisor on a Windows operating system and the results showed VMware performed better. Bara says the comparison was not fair because Open Source Xen is optimized to run best on Linux, not Windows. XenSource's Xen Enterprise product is optimized to run Windows and would be a more balanced comparison to VMware's ESX.

"We cooperate with VMware in a lot of areas, but we went back to them and said 'foul,'" said Bara. To VMware's credit, he said, it redid the test and accepted the revised benchmark that showed VMware ESX and Xen Enterprise with nearly comparable performance.

Also Monday, XenSource entered into an OEM agreement with Symantec Corp. to embed Symantec's Veritas Storage Foundation virtualized storage management software into Xen Source's XenEnterprise virtualization hypervisor.