Avance runs on top of a customized version of the Citrix XenServer virtualization platform, providing fault tolerance to any Windows or Linux guest running on either of two physical servers -- at substantially lower cost than other high-availability solutions. Installation and management are straightforward, and delays in server responsiveness during a failure proved minimal in our testing: less than a second in the case of Linux, and only four or five seconds for Windows Server 2003 running Exchange Server.

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