The main beneficiary of the x86 virtualization trend has been VMware, which remains far and away the leader in this space. However, two alternatives based on the Xen virtualization engine – Virtual Iron and XenSource – have emerged as legitimate contenders to VMware. Both now sport advanced management features and Microsoft Windows support.

In August 2007, Xen received a further legitimacy boost when application delivery vendor Citrix announced a $500 million plan to acquire XenSource. In making this move, Citrix is bolstering its position against increasing competition from virtualization solutions. XenSource, which has a client base of about 750, is expected to greatly benefit from access to Citrix sales channels and large current customer base.