Among the biggest trends today is server virtualisation. And while EMC subsidiary VMware has garnered the most attention, a whole slew of vendors are looking to address what they see as rising demand for this server consolidation technique.

At the top of that list is Microsoft, which earlier this fall aired plans for Virtual Server 2005. Like other server virtualisation technologies, Virtual Server 2005 lets users divvy up servers so that they can support multiple operating system instances and applications. The software, scheduled to ship next year, is based on technology obtained via the acquisition of Connectix early last year that works on Windows, Linux and Macintosh servers and workstations.

Also entering the market are a gaggle of lesser-known players, such as Leostream and PlateSpin , whose products offer management, security and other such capabilities for virtualised systems.

"Virtualisation is moving from a niche market into the mainstream, especially since Microsoft entered the market," says David Crosbie, CEO of Leostream, whose software manages virtualisation servers attached to storage area networks (SANs).

But it is VMware, which EMC paid $635 million to acquire earlier this year, that sparked the server virtualisation movement. Recently, the EMC subsidiary held its first annual customer conference, where VMware and others announced the latest developments in server virtualisation.

VMware announced that it would extend the capabilities of its Virtual SMP offering to dual-core and four-processor symmetrical multiprocessing servers. The company, which already offers dual-processor SMP software, is doing this for two reasons. First, VMware officials say that even though most server workloads run fine on two-processor servers, 15 per cent to 20 per cent of customers require machines with four processors. Also, VMware is trying to keep pace with next-generation servers powered by AMD and Intel processors.

"If you look at processor trends, both Intel and AMD have shifted from increasing the clock speed of their processors to increasing the number of processor cores on a single chip," says VMware marketing manager Michael Mullany. "Going forward, you are going to find out that even a two-CPU server actually has four processors."

VMware, which was founded in 1998, has partnerships with Citrix, Dell, HP, IBM, Oracle and Red Hat, among others. Gartner says VMware owns the bulk of the virtualised server market and will control about 80 per cent of it by the end of next year, though the research firm figures Microsoft will start to challenge VMware over the next couple of years.

Here's a look at some of the other companies vying for attention in server virtualisation:

Leostream, a VMware partner, started in 2001 and makes the Virtual Machine Controller (VMC). The software is designed for managing server virtualisation products from VMware and Microsoft, presenting each virtual server on a Web-based display. Its latest offering, VMC SAN edition, is for managing virtualised servers attached to a SAN. It costs $2,800, plus $300 per processor managed.

"One of the biggest features of Leostream's VMC SAN Edition is the ability for your virtual machines to fail over," says Leo Frisino, computer systems programmer for the New York State Division of Housing and Community Renewal in Albany. "If a virtual machine is executing in a server and that box fails, the virtual machines will come up on the other ESX box. VMware does not have similar failover capability," says Frisino, who virtualises five production servers with VMware's ESX Server.

PlateSpin recently launched software that lets IT automatically convert Windows and Linux servers back and forth from physical servers to virtualised servers. PlateSpin's PowerP2V 3.6, which runs on a desktop PC, starts at $3,000 for a version that allows 25 conversions.

Softricity has partnered with Aurema to let customers manage, streamline and optimise their virtual machine environments running VMware's ESX Server and Citrix MetaFrame. Softricity's software enables applications to be spread across virtual machines, while Aurema's ArmTech is workload management software that monitors, optimises and dynamically allocates processors and memory for applications running in virtual machine environments.

Dave Williams, senior systems engineer for the US-based Government Employees Hospital Association, uses ArmTech on his servers to balance application loads. "Once our Citrix servers were rebooting, locking up and had the processors running to 100 per cent," he says. "ArmTech balances the workload of applications with the [server's] memory and processor, so one user can't steal 100 per cent of the processing capability."