Xen is the flavor of the month in the tech world. Not only is the open-source technology supported in the new release of Novell's Suse Enterprise Linux distribution, but Microsoft pledged to support Xen-virtualized Linux with its forthcoming Longhorn server virtualization technology. And don't forget about IBM.

Big Blue joined the Xen-fest last week, too, announcing that its low-end servers and middleware will support Xen via the new Suse release.

The announcements move XenSource closer to the goal of having Xen 3.0 hypervisor on the majority of x86 hardware and operating systems, said Simon Crosby, XenSource CTO.

Sun has already committed to support Xen in its OpenSolaris operating system this year, and in Solaris in 2007. Red Hat said it will support Xen in its new Enterprise Linux 5 distribution, due out this December.

As Xen moves more into the mixed workload environment, however, it's bumping into market incumbent VMware. VMware Vice President Brian Byun publicly dismissed XenSource's tie-up with Microsoft as a "one-way street" that favors Microsoft. XenSource's Crosby countered, calling VMware's characterization "the gut reaction from a wounded animal."

Both technologies have advantages, according to Tony Iams, a senior analyst at Ideas International: Xen has open source credentials and performance benefits from paravirtualization; VMware is a mature and tested technology and offers high availability and disaster recovery.

Where is this all leading? Over time, all the virtualization functionality provided by paravirtualization and hypervisors will be standardized, Iams said.

At that point, the battle moves to virtualization management, in which VMware has an early lead. But there will be a host of players vying for a slice of the virtualization management pie, too. Look for server, systems management and open-source vendors, not to mention users with homegrown wares, Iams said.