XenSource's release is XenExpress. Like, it lets multiple operating systems run simultaneously in separate compartments, called "virtual machines," on the same server. Unlike XenEnterprise, however, it allows people to manage only one virtual machine at a time.
of its competing software, which now supports Microsoft Windows as well as Linux. The company offers the product at no cost for single servers with as many as four processor sockets. However, it charges $499 per socket for software that lets customers manage the virtualization software running on groups of servers.
While the two companies compete against each other, their primary rival is VMware. The EMC subsidiary pioneered virtualization software on servers using x86 processors such as Intel's Xeon and Advanced Micro Devices' Opteron. It has a major market presence.
Xen relies on Linux and can run it gracefully. Running Windows, however, requires hardware features in newer AMD and Intel chips. XenSource's Windows-specific virtualization product is called XenServer.
Virtualization is catching on today primarily as a way to consolidate several servers onto a single machine, which increases efficiency. However, advocates point to advantages it offers in making it possible to quickly start up new systems and in making server applications more flexible, so they can adapt to changing workload demands.