Quoting eWeek 

Virtual Iron Software's Virtual Iron builds on the Xen hypervisor and other open-source components to form an effective virtualization solution with a price tag low enough to keep market leader VMware on its toes.

During tests of Virtual Iron 3.5, eWEEK Labs was particularly impressed with the product's provisioning capabilities: We simply plugged our virtualization host servers into a management network, and PXE (Preboot Execution Environment) booted them from Virtual Iron's management server. Once the servers were up, we could begin creating and assigning virtual machines to our nodes right away.

One of the biggest differences between Virtual Iron 3.5 and early Xen-based virtualization products is Virtual Iron 3.5's ability to virtualize pretty much any x86- or x86-64-based operating system—without a special, Xen-aware kernel.

Virtual Iron and other current Xen-based virtualization products manage this modification-free virtualization by running on top of Advanced Micro Devices and Intel processors that feature AMD-V and Intel VT hardware extensions, respectively.

Most notably, this hardware support brings Windows within Xen's ken, a capability that VMware's products have long enjoyed. However, unlike XenSource's XenEnterprise, Virtual Iron 3.5 offers no option for running on hardware without virtualization extensions, which could be a problem if you're hoping to tap virtualization to squeeze more out of your existing machines.

However, the hardware extensions on which Virtual Iron relies are becoming de rigueur for most machines. What's more, after taking into account Virtual Iron's cost advantages over VMware's products, enterprises that choose to go with Virtual Iron might find that they can afford to make some hardware purchases with their savings.

The full-featured enterprise edition of Virtual Iron 3.5—which includes live migration, failover and capacity management functionality, as well as support for Fibre Channel SAN (storage area network) and iSCSI storage—costs $499 per socket. VMware's VI3 Starter is priced similarly—at $1,000 per pair of CPU sockets—but it lacks support for SAN or iSCSI storage. VMware's VI3 Standard sells for $3,750 per pair of CPU sockets; VI3 Enterprise, which adds support for VMotion live migration and other high-availability features, costs $5,750 per pair of CPU sockets.

We tested Virtual Iron 3.5 Enterprise Edition using the free, 30-day trial license. Also available is a free, single-server version of Virtual Iron, in which the management server and virtualization host live on the same machine.

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