The last few weeks many blogs and forums have spend time on hypervisor comparisons and I have read tons of articles on the subject. Many only compare hypervisors based on performance, features or cost. I think it’s a bit more complicated then that. After Citrix announced that their XenServer product is available for free I spend a fair deal of my time explaining to colleagues and clients that this is a hoax and that cost is not the only reason to base their decision on. Especially in the case of XenServer the choice and the long term effects make it a little bit more complicated.

When I read Chris Wolfe’s article on ‘Production-class Hypervisor Evaluation criteria‘ and saw his VMworld Europe 2009 presentation (DC15) I found someone who read my mind. Chris knows what he is talking about and uses the right criteria to select the right hypervisor for the job. Now you probably think ‘These guys are VMware fans so here we go again‘ but the opposite is true.

Like Chris I think every situation has its own ideal solution and you should select the hypervisor based on well-considered selection criteria and because my employer, Centric, focuses on clients with 500+ workstations/employees these criteria are Enterprise-class hypervisor selection criteria.

Hereby a selection of my most important Enterprise-class hypervisor selection criteria.

  1. Can this hypervisor support your business needs and long term strategy for the next 5-10 years as it is one of the infrastructures core components which requires investment;
  2. Support for advanced network features, like:
    • VLAN tagging (802.1q);
    • Link aggregation (802.3ad);
  3. Guest operating system support;
  4. Support for VMotion/Live migration without service interruption;
  5. Support for integrated storage features;
  6. Performance;
  7. Scalability;
  8. Migration tools;
  9. Integration with organizations management tools, like SCOM, HP Openview;
  10. Integration with directory services like Active Directory or NDS;
  11. Integration with the enterprise back-up solution;
  12. High Availability preferably without any downtime for business critical services;
  13. Support for hardware assisted virtualization support;
  14. Multi interface storage support (FC, iSCSI) for flexibility;
  15. Extensive logging options to aid in trouble shooting;
  16. Support for multi processor virtual machines equal to the most up-to-date x86 server;
  17. Support for large memory virtual machines equal to the most up-to-date x86 server;
  18. Management is/has a:
    • High Available;
    • Client based console;
    • Web based console;
  19. Following support options are available:
    • 24×7;
    • 12×5;
    • 1-3 years;
  20. Paravirtualization support;
  21. Memory management
  22. Security

These criteria should be divided in two categories, ‘need to have’ and  ‘nice to have’. If a hypervisor does not meet the criteria which it needs to have, it disqualifies as an Enterprise ready hypervisor.

Beware to do a good and fair comparison by function and not just by name. As we described at the end of March some Citrix ‘experts’ tend to compare VMware HA to Citrix XenMotion and claim their free version include high availability.

The last weeks Anne Jan and I spend a lot of time in creating the hypervisor comparison below.


We tried our best but Hyper-V and XenServer information had to be based on information on the Internet as we do not implement these two very much. If we made a mistake or you have an addition, please let us know. We want to provide you with a correct comparison.

After you have evaluated all hypervisors according to the selection criteria, the next step is to differentiate hypervisors by the total cost.

This is cost for a complete Enterprise solution including:

  • hardware;
  • software;
  • support;
  • cost savings per year.

To keep this comparison fair it should only include the components needed for an enterprise solution as described in your selection criteria. So this includes high availability, resource scheduling and live migration.

When you have the cost discussion with colleagues or client it is often polluted by the free software myth. Like Edwin wroteThere is no such thing as a free lunch‘. All major hypervisors have a free version but these free versions are very limited now and/or in the future. A good example is the free version of XenServer which Citrix announced at the end of February. According to Citrix it is a free enterprise solution but this 4.5 version will be replaced by the new 5.0 version at the end of March and this new version will lack enterprise functionality like high availability.

When you have made your hypervisor selection and the total cost is clear, you can add a third and final option, that is can you add additional features like disaster recovery, chargeback, monitoring, etc.

Good luck finding the ideal hypervisor for your situation.

Update 04-06-09: Linked the new v1.3 comparison sheet.

Last update: November 29th, 2011.