http://searchservervirtualization.techtarget.com/tip/How-to-configure-Citrix-XenServer-live-migration

http://support.citrix.com/servlet/KbServlet/download/27046-102-666250/XS-design-network_advanced.pdf

http://opentodo.net/2012/10/xenserver-ha-live-migration/

• Live migration is a free feature
• No need for an additional purchase
• Virtual disk of the VM being migrated has to be on shared storage
• You must have installed the Xen Tools package in the VM

I haven't had much luck with storage live migration yet.

http://www.citrix.com/content/dam/citrix/en_us/documents/products-solutions/storage-xenmotion-live-storage-migration-with-citrix-xenserver.pdf