Red Hat is preparing to release version 6 of its free Fedora Core Linux operating system next month.

The updated system includes version 3.0.3 of the open-source Xen virtualisation software, which was originally scheduled for release early in July. Companies can use server virtualisation to consolidate multiple workloads onto a single server, thus saving money on hardware, space and power.

Roger Klorese, product director at XenSource, the company behind the open-source Xen software project, told IT Week, “We decided to synchronise the release of 3.0.3 with the Fedora Core 6 schedule and hence push it back... It now has several of the features that were originally slated for 3.0.4.”

Unlike VMware ESX Server 3, which is used by many organisations to host mission-critical applications, Xen is still very much a work in progress. Consequently each Xen release brings major features that should eventually enable it to compete with alternative virtualisation offerings.

Xen supports two virtualisation methods. When used with processors that include hardware support for virtualisation, Xen can host a wide range of operating systems, including Windows and Linux. However, Xen also has a para virtualisation (PV) mode for other processors, which can virtualise operating systems only if they have been specially modified to work with Xen. The list of specially modified software includes some Linux distributions but excludes Windows.

XenSource had previously said most of the changes in 3.0.3 affect Xen’s PV capabilities. The update includes optimisations to improve para virtualised USB and network performance, and a PV frame buffer that enables graphic displays of virtual machines (VMs).

The release is also expected to include a new CPU scheduler and support for a basic non-uniform memory access (Numa) memory allocator.

Klorese said the 3.0.4 release of Xen is expected before Christmas. “Version 3.0.4 should appear eight to 12 weeks after 3.0.3. We’ve loosened the spacing up a bit from the eight-week [release cycle] I talked about previously,” he added.

Earlier this year Klorese said version 3.0.4 would be optimised to run on servers fitted with four CPUs. Xen supports VMs configured with 32 CPUs, but most users will run Xen on four-way systems.