XenSource has released version 3.0 of its Xen virtualisation software, the first major open-source offering to compete with the likes of VMware, Scalent and SWsoft.

At the same time, it also produced its first commercial offering, XenOptimizer, for managing virtualised deployments.

Virtualisation allows multiple instances of an operating system to run on a single machine, with cost and management benefits for system administrators. Xen's system is designed to offer high performance for large numbers of operating system instances, with the shortcoming that operating systems have to be modified to run with the Xen virtual machine motitor (called a hypervisor).

Xen 3.0 can take advantage of the Virtualisation Technology (VT) support built into recent versions of Intel chips - and soon with AMD's Pacifica - which eliminates this limitation, allowing virtualisation of unmodified operating systems (such as Windows).

Other features include support for up to 32-way SMP systems with the ability to "hot plug" CPUs, and two new addressing modes for servers with large memories. Physical Address Extension (PAE) allows 32-bit servers to address more than 4GB of memory, while support for Trusted Platform Modules adds hardware-based security.

As with previous versions, the software supports the relocation of a running guest OS from one physical server to another.

An Itanium port is included, and a PowerPC port is near completion, according to XenSource.

XenOptimizer is the first bid of XenSource - founded by the software's original developers - to make money from the project. It is aimed at enterprise data centre environments, and competes with support already offered by the likes of IBM and HP.

Scalent, SWSoft and Microsoft all recently introduced competing virtualisation systems for the data centre.

SWSoft recently introduced a new version of Virtuozzo for Windows that supports the same features as the company's Linux version. Microsoft announced an update to Virtual Server that adds some features and formalises Linux support. Both, like Xen, are designed to allow multiple instances of a server to run on a single machine.

Scalent's Virtual Operating Environment (V/OE), introduced this month, takes a different tack to increase server utilisation, aiming at better managing the commodity servers now filling most data centres. V/OE is designed to deal with the problem of "server sprawl" by allowing administrators to treat heterogeneous servers, networks and storage as a single fabric.