High Availability
(高可用性)

http://www.citrix.co.jp/xs5_micro/ha.html

http://www.xenserver5.com/ha.php

http://docs.xensource.com/XenServer/5.5.0/1.0/en_gb/reference.html#id2505080

http://community.citrix.com/blogs/citrite/anilma/2008/09/17/Peeking+under+the+hood+of+High+Availability

XenServer System Recovery Guide
http://support.citrix.com/article/CTX117257