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KVM vs. VMware: A Case Study

After a month of debate and experimentation, my employer has made the decision to use the open-source KVM virtualization infrastructure for migrating IT resources to a virtualized environment.  Below, I discuss why we chose KVM over its (mostly proprietary) alternatives.

Christopher Tozzi

April 27, 2009

3 Min Read
KVM vs. VMware: A Case Study

After a month of debate and experimentation, my employer has made the decision to use the open-source KVM virtualization infrastructure for migrating IT resources to a virtualized environment.  Below, I discuss why we chose KVM over its (mostly proprietary) alternatives.

Until a couple years ago, the open-source community offered no real contender in the virtualization market.  True, the qemu project has been around for a while, but qemu remains too inefficient for most production environments.  Xen has also existed since 2003, but for a long time it only supported a limited set of guest operating systems, which did not include Windows until late 2005.  As a result, proprietary virtualization products like VMware enjoyed a near-monopoly in the enterprise market until quite recently.

The rapid maturation of KVM, or ‘kernel-based virtual machine’, over the course of the last couple of years constituted the first open-source challenge to VMware.  Integrated into the Linux kernel, KVM provides feature-rich and highly efficient virtualization.

My colleagues and I tested KVM (running on an Ubuntu 8.04 host) and ‘barebones’ VMware ESX server over the last several weeks.  Ultimately, we decided KVM was a better fit for our needs based on the following considerations:

  1. Cost.  Although our virtualization requirements are minimal–we need to run only two guest servers on a single host machine–VMware would have cost an astonishing amount of money.  With features like VMware motion factored in, we were looking at a huge hit to the budget–and it didn’t help that VMware charges per CPU, not machine, regardless of whether all CPUs will actually be dedicated to virtualization.  KVM is totally free, in both senses of the word, and offers functionality equivalent to VMware motion.

  2. Ease of deployment.  Installing KVM on Ubuntu 8.04 is as simple as an apt-get.  ESX server is also easy enough to install, but having to deal with licensing adds another layer of complication that we’d prefer not to face.  KVM, of course, requires no license.

  3. Speed.  Although I don’t have hard numbers, KVM-based virtual machines definitely ‘felt’ more responsive than those running on VMware.  Our experience seemed to confirm Red Hat’s claim last fall that KVM can support five VMs for every three running on VMware on the same piece of hardware.  It was also troubling that ESX server wasted upwards of 500 megabytes of memory–without any VMs running–on system overhead, while an Ubuntu server is a considerably more efficient host.

  4. Management.  Apparently it never occured to VMware that systems administrators might be running Linux on their workstations.  As a result, Windows is the only platform on which VMware’s graphical management infrastructure is supported.  A Linux CLI client is available, but I’d like more options than that.  KVM, in contrast, can be managed via the command line, via graphical interfaces (running either on the local machine or forwarded over ssh to a remote workstation) or through the Enomaly web interface.

Perhaps the single major downside of KVM is that it requires a bit more technical know-how than VMware to deploy effectively, since some features can only be configured via manual hacking of XML files.  But as KVM and related tools continue to mature, expect that to change.

For IT staff interested in zero-cost, Linux-friendly, feature-rich and resource-efficient virtualization, KVM has become the way to go.  If VMware wants to compete, it needs to rise from the laurels of its crumbling monopoly by innovating and lowering costs.

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About the Author(s)

Christopher Tozzi

Contributing Editor

Christopher Tozzi started covering the channel for The VAR Guy on a freelance basis in 2008, with an emphasis on open source, Linux, virtualization, SDN, containers, data storage and related topics. He also teaches history at a major university in Washington, D.C. He occasionally combines these interests by writing about the history of software. His book on this topic, “For Fun and Profit: A History of the Free and Open Source Software Revolution,” is forthcoming with MIT Press.

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