There are real differences among the various virtual machine (VM) products for x86 servers. Prices and business models vary widely, but each supplier monetises virtualisation through the hypervisor, management, support or operating system software. In a market that is in flux, Gartner continues to recommend deployments with a rapid return on investment, and fallback plans to migrate to alternative technologies if necessary.
VMware stood alone in the x86 server VM market since 2001, but competition will offer alternatives with less functionality at a lower cost. VMware will be challenged to adjust its business model while maintaining high growth. VMware's edge over the competition is its large installed base, proven technology, deep virtualisation management capabilities (including VMotion) and small footprint - ESX Server 3i is 32Mbytes. Owing to its small footprint, VMware is less vulnerable to security breaches, less susceptible to stability issues and easier to maintain. The majority of companies that deploy VMs during the next several years will continue to have physical server images, but VMware's current software cannot manage them.
Prior to its October 2007 acquisition by Citrix, XenSource was the leader in open-source Xen development, building a commercial product around the Xen hypervisor and employing the majority of key Xen developers. The Xen hypervisor's primary differences from VMware were that it was open source and versions were available for free. Citrix XenServer has been available since December 2006, and with several thousand customers, it is relatively mature. However, we have not seen enough XenServer deployments in mission-critical roles. Therefore, its vulnerability is still in question. As with all Xen-based offerings, XenServer's third-party software support is still limited. For customers that already have an effective working relationship with Citrix, XenServer is a solid choice, and the interoperability agreements with Microsoft make the investment safer and easier to migrate if needed.
Oracle announced the availability of free a Oracle VM, based on Xen, in November 2007, with plans to integrate VM management into Oracle Enterprise Manager in 2008. Although Oracle touted the security and performance of its product, Oracle VM's real differentiators are that it is supported by Oracle (the supplier does not certify its products on alternative hypervisors, and product support on alternatives is limited) it will be managed by Oracle Enterprise Manager and Oracle also can deliver its business applications as downloadable VM templates, with everything customers need to get up and running in virtual environments (operating systems, patches and so on). With Oracle's focus on enterprise customers, Gartner believes that it will deliver a more secure system than smaller, Xen-based suppliers.
Sun announced xVM Server in late 2007, with availability expected in mid-2008. By the end of 2008, the product will still be relatively new, so maturity and support are expected to be limited. However, using Solaris as the management console, Gartner expects that Sun will do a good job with security. Sun also announced xVM Ops Center for VM management, which was released in January 2008. However, this lacks VM management capability until xVM Server is released. Pricing for xVM Ops Center is relatively low - £50 to £175 per server managed per year. Pricing for xVM Server has not yet been announced. Gartner expects xVM Server pricing to be low as well.
Microsoft's differentiation strategy will be to go "above" VMware's management by integrating the System Center family of products with virtualisation management, which supports its Hyper-V product. Unlike VMware's new thin hypervisor architecture, Hyper-V relies on a running copy of Windows Server 2008 - at least the Server Core subset. Drivers and driver operations are managed through Windows Server 2008. If that copy of Windows goes down, is attacked or requires patches, then all VMs on the server will be affected. Microsoft's solution is to have a rock-solid Windows Server Core, which is certainly possible. But given its size, it will be a challenge. Furthermore, Microsoft is enabling users to use the full Windows Server 2008 "personality" as a parent OS, including the freedom to install any applications the user chooses. This kind of flexibility is dangerous for a single point of failure.
The bottom line is that this year, users have real choices. Competitive pressure that will bring prices down and ensure continued enhancements. Product maturity is certainly important, but ease of management of a growing number of VMs will be the most important selection criterion.