Quoting from the XenSource official announcement:
Marathon Technologies Corporation, the leading provider of automated, fault tolerant-class availability solutions for virtual and physical environments, today announced a strategic and technology-based partnership with XenSource, the leader in infrastructure virtualization solutions based on the open source Xen hypervisor.
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The partnership with XenSource supports v-Available, Marathon’s initiative designed to drive the convergence of high availability and virtualization technologies. Marathon applied its 12 availability patents and over 14 year experience in engineering availability software solutions to the development of v-Available. With this new initiative, Marathon is aiming to fill significant gaps in current high availability offerings for virtual environments…
Marathon and XenSource are working together to deliver a series of products, the first expected in the second half of 2007, but fundamentally the announcement is stating Marathon HA solution for operating systems, everRun, is going to be supported inside XenSource virtual machines.