The other day I saw someone post a poll question, â€œIs KVM a credible choice for x86 virtualization?â€ My immediate response was â€“ â€œIs that even a credible question?â€ If you read my many contributions to TechTarget, you will know I am no great supporter of KVM (Kernel Virtual Machine). In my analysis, it does not offer any significant advantages to the many alternatives. It does, however, introduce many significant challenges.
The only significant and unique benefit of KVM for server virtualization (as noted by Sander van Vugt in our (virtual) debate on Xen vs.KVM Linux Virtualization Hypervisors) is that KVM is part of the Linux kernel. This ensures broad standardization, patch compatibility, simpler upgrades, and a low-impact on-ramp for existing Linux IT shops.
Yet this is a solution for a problem that does not really exist.
Large enterprises already run thousands of components, from services/daemons to drivers to applications, all as additions to various kernels. Maintaining one more (or even several more) non-kernel components like Hyper-V, XenServer, ESX, etc., is not a net negative. On the contrary, EMA data shows that virtualization actually improves the productivity of server administrators, and by an average of around 10% – up to 20% or more for best performers. For competent administrators with good lifecycle management tools, the time they spend to learn, test, and maintain hypervisors is a significant effort, but it is time paid back with interest.
On the other hand, many downsides to KVM are all too apparent.
It is easy to point to the lack of technology features and maturity in KVM – areas like live migration, paravirtualization, networking, isolation, performance, security, or a host of otherÂ features which KVM (in some cases arguably) lacks. I have only some doubt that KVM will meet these low-level functional requirements eventually, but it will not be anytime soon. Yet they are essentially table stakes in server virtualization today.
The inherent dependency on Linux would also require a major shift inÂ platforms for the average datacenter (where Windows outnumbers Linux byÂ 150:1), and a major investment in resourcing, training, and software. This is hardly an attractive proposition for a data center manager. Still, existing Linux staff will be able to pick it up, and could even have some success on their (relatively few) existing Linux platforms.
However, even if these weaknesses are overcome, KVM has a much more strategic problem – the gaping void in the KVM management ecosystem. There is almost no third-party support for KVM from management vendors. Even stated support from key partner vendors like IBM, HP, and of course Red Hat is basic at best. What’s more, EMA data suggests KVM will not foster a significant management ecosystem in the future, either.
EMA’s research on Virtual System Management showed convincingly how important management is to virtualization. Across 18 different management disciplines, almost all correlated with measurably better outcomes in metrics like MTTR, provisioning time, availability, VM density, migration speed, and more.
EMA’s new cloud research shows a similar importance. Applying mature automation and management disciplines to virtual systems is directly correlated with positive cloud outcomes like reduced CapEx, reduced OpEx, improved operational maturity and more.
Not surprising then, that over 80% of enterprises consider manageability an important or very important factor in their virtualization and cloud technology decisions.
Unfortunately, KVM ranks anywhere from 4th to 10th in enterprise preferences for virtualization and cloud technology providers. It comes behind first ESX, then Hyper-V or Xen (multiple implementations), often various UNIX hypervisors (PowerVM, Integrity VMs or vPars, Solaris Containers), and even z/VM. No enterprise demand means that management vendors have little incentive to support KVM.
In fact, in my conversations with management software vendors, most generally put KVM around 5th in line for support – which, realistically, means it is not even on the current roadmap. What’s more, for better or worse several of them have a vested interest in not supporting KVM (no points for guessing who).
This means KVM has little or no prospect of gaining third-party support for virtualization management tools like VM-aware backup and restore, VM provisioning, virtual resource management, VM configuration auditing, virtual performance monitoring, VM lab management, VM image control, storage management,network automation and more. The same holds true for integration with higher-level virtual systems management tools for virtual and physical data center automation and service management disciplines.
For any IT group, sophisticated management tools deliver many proven benefits. For larger enterprises especially, they are simply not optional.Â Without even the prospect of a robust management ecosystem, KVM is simply a non-starter in most large-scale deployments. For my enterprise clients at least, it is certainly not a credible choice for x86 server virtualization.