The two companies, which originally disagreed on how to build support for virtualization into the Linux kernel, are committed to working together on a common approach, says Simon Crosby, CTO at XenSource, the company that builds products around Xen virtualization software. "With the help of IBM, we made a technology breakthrough that accommodates both," Crosby says.
XenSource and VMware got together at the Linux Symposium held last month in Ottawa to start work on an interface to the Linux kernel, says Jack Lo, VMware's senior director of research and development. "There's been a lot of activity" to reach agreement, he says.
The goal is to let different hypervisors manage Linux virtual machines generated by a competitor's software. Hypervisors are a second generation of virtualization software that provide a more efficient way of running virtual machines on a server.
Open source Xen, first produced in research at Cambridge University, England, is a hypervisor, as is VMware's ESX Server. Microsoft is working on a hypervisor, called Viridian, due in late 2007 or 2008.
Data center managers frequently turn to virtual machines to consolidate multiple servers on one piece of hardware. The strict software boundaries of virtual machines let different and sometimes incompatible applications run alongside each other on one piece of hardware, reducing the demand for new servers.
The work under way would let hypervisors from Microsoft, VMware, and Xen work together in the same data center. It would be possible for a Xen virtual machine, trapped on a piece of failing hardware, to be automatically moved to a VMware hypervisor on another piece of hardware.
The ability to manage failovers and do backups and recoveries would be enhanced if the Linux kernel were given one method of dealing with all hypervisors, says Carlos Montero-Luque, VP of Linux product management at Novell.
VMware and XenSource have different hypervisor designs and initially disagreed on how to construct a Linux kernel interface. VMware has proposed what it calls a Virtual Machine Interface to the Linux kernel that works well with ESX Server. But Rusty Russell, a Linux kernel developer at IBM, came up with a proposal in Ottawa that accommodates both Xen and ESX Server, Crosby says. VMware and XenSource are collaborating on Russell's idea, called Paravirt_ Ops, or paravirtual operations.