Virtualization Shootout: VMware Server vs. VirtualBox vs. KVM
Virtualization is a buzzword that's been making its way around the corporate IT circles for a few years. On paper, virtualization sounds great—you can make full use of those unused CPU cycles, leverage a particular machine to its fullest potential, and save power and space at the same time. Many people think virtualization is good only in the corporate data center; however, several software packages run just fine on desktop- and laptop-class Linux machines, as well as servers. In this article, I put three of them through their paces: VMware Server, VirtualBox and KVM.
“But wait!” you may exclaim, “Why aren't you evaluating Xen too?” The answer is simple. Xen, although extremely powerful, is more of an enterprise-class virtualization solution and may be overkill for the average Linux user. If you're going to be building a data center or a service that will be exposed to customers on the Internet, that's when you should consider Xen. This is one of the reasons Ubuntu officially supports KVM, rather than Xen, as its open-source virtualization solution, and I follow that reasoning here.
First, I should define a couple terms for the purposes of this article. A host is a physical machine running one of the virtualization solutions. A guest, virtual machine or VM is the virtual machine running inside the virtualized container provided by the host.
Because this is a shootout, I assign point values to categories, and the product with the most points wins the shootout. The values range from 1 to 3, with 1 being poor, 2 being average and 3 being excellent. All of the virtualization packages are installed on an Ubuntu 9.04 host. The categories are as follows:
Ease of installation.
VMware has been providing virtualization solutions for ten years, and as such, is the virtual 800-pound gorilla in the marketplace. With at least six virtualization products that span both the desktop and server markets, VMware has a package that will fit your needs. The product I review here is VMware Server 2.0. It's free (as in beer) and is very feature-rich.
Ease of Installation
VMware Server ships as a 507MB Windows executable, a 465MB RPM or a 466MB tarball. Because I'm installing on an Ubuntu machine, I use the tarball. Kicking off the installation is fairly straightforward on Ubuntu. Simply ensure that you've got the build-essential package installed, along with the headers for whatever kernel you're running. Then, untar the tarball and run ./vmware-install as root, and follow along with the prompts. The installer will prompt you for the paths to where you want to install various things. It's acceptable to choose the defaults, as the installer chooses fairly sane locations.
One thing to note is that due to VMware's “free as in beer” license, you must get a serial number from the VMware site before you can run it. Make sure you have registered on the VMware site and have your serial number handy, as the installer will ask you for it near the end of the installation process.
Ease of installation score: 2. This is mostly due to VMware requiring some packages and asking many questions in the installer. It works well once you get it installed, and you can take the defaults on just about every question, but it is a little tedious.
If you've used VMware Server 1.0 and haven't looked at 2.0 yet, you're in for a surprise. The 2.0 version of the product uses a Web-based administrative panel, compared with the “fat client” approach that the 1.0 product used (Figure 1).
Everything in the admin console is easy to use. Creating a virtual machine is a simple matter, thanks to VMware's excellent form-based wizards. Simply fill in the blanks, and VMware will create an appropriate VM and get it ready for its first boot. VMware Server provides a virtual console via its Web interface to the virtual machine as well (Figure 2). It requires installing a Firefox plugin, but the console works well and doesn't require a fat client. Unfortunately, the plugin doesn't work on the Mac version of Firefox.
VMware also allows you to console to the machine remotely via VNC. This requires adding the lines RemoteDisplay.vnc.enabled = "TRUE" and RemoteDisplay.vnc.port = 5900 to the virtual machine's configuration file (named <hostname>.vmx in the virtual machine storage directory).
In short, the VMware administrative console is excellent. The Web-based GUI is easy to navigate, and the tools work well on Linux or Windows. The ability to enable VNC access to a virtual machine's console without using the Web GUI could prove invaluable in certain administrative cases.
Administrative tools score: 3. VMware's experience in the field shows here, and VMware Server's historical connections to the GSX commercial product mean that the tools are best of breed.
VMware Server is an extremely capable virtualization platform. Its ancestor is VMware's first-generation commercial server product, VMware GSX, so it has a great pedigree. VMware Server's key features include:
The ability to run on standard x86 hardware, with or without hardware virtualization extensions.
Two-processor Virtual SMP, allowing a single virtual machine to span two processors.
A snapshot feature, allowing you to capture the state of a VM and then roll it back to that state.
64-bit support, on both the host and guest operating systems.
Support for bridged, NAT and host-only network interfaces.
Support for USB devices and controllers.
All these features mean that VMware Server is a great platform for personal experimentation or light business use. I've personally had a VMware Server host with a couple guest machines running continuously since 2007.
Capabilities score: 3. VMware has been building its feature set for years, and it shows here.
VMware Server has a proprietary license with appropriate EULA for this software. Although it's technically free, it's “free as in beer”, meaning that though it costs nothing, you can't actually modify it. VMware does make some source code available, but it's not the entire source tree, only the parts that are GPL that VMware modifies. In order to use the software, you need to register on the VMware Web site and get a serial number in your name. Although this is available at no cost, it isn't “free” in the open-source sense.
Licensing score: 1. VMware's proprietary license and EULA mean you can't lift the hood and tweak it as you see fit, nor can you analyze the code for vulnerabilities. You're at the mercy of VMware. If Free Software is important to you, this license will give you fits.
VMware Server total score: 9.
Bill Childers is the Virtual Editor for Linux Journal. No one really knows what that means.