VMware GSX Server 2.5 is one of a few virtual machine (VM) products that VMware offers. Other products in the company's lineup include VMware Workstation 3.2, VMware ESX Server 1.5.2 , and VMware Virtual SMP. VMware Workstation is for technical professionals who want to run Windows and Linux OSs but who don't need to support SMP hosts. At the other end of the spectrum, VMware ESX Server is for high-end mainframe-class systems. VMware ESX Server provides better performance and scalability than VMware Workstation by directly partitioning the hardware into VMs and resources without the need for a host OS. VMware ESX Server supports the Windows and Linux server OSs. At the time of this writing, VMware had yet to release VMware Virtual SMP. Like VMware ESX Server, VMware Virtual SMP implements a virtualization layer directly on the hardware platform with no host OS and lets the VM use multiple processors.

VMware is probably the best-known VM vendor, but it's certainly not the only one. Connectix (http://www.connectix.com), which Microsoft recently acquired, is a well-established company in the Windows VM market. Connectix offers Virtual PC for Windows, Virtual PC for Mac, and its upcoming Virtual Server product, which Microsoft will finish. Virtual PC for Windows 5.2 runs on Windows XP Professional Edition, XP Home Edition, Windows 2000 Professional, and Windows NT 4.0 platforms and lets you run almost any Intel-based OS, including other versions of Windows, Novell NetWare, OS/2, UNIX, and Linux. As its name implies, Virtual PC for Mac runs on Mac OS X and OS 9, and the software lets Macintosh users create Windows desktop and DOS-based VMs. The Virtual Server product will provide SMP host support and enable the virtualization of the Windows server products.

Non-Windows products in the VM market include SWsoft's (http://www.swsoft.net) Virtuozzo 2.5 and Ensim's (http://www.ensim.com) Virtual Private Server. Virtuozzo and Virtual Private Server provide a virtual environment for Linux and UNIX servers.