experience configure citrix xenserver migration

a few important about configuring citrix xenserver live migration:

set up NFS share resource between xenserver hosts:
- my host running Xenserver 5.6 service pack2. setting up nfs was not easy as service using portmap or dynamic port, making setting firewall iptables rules difficult. => solution: in nfs config file, set static port and set corresponding firewall rules to open those ports.

set up live migration of vm between xenserver hosts:
- storage for vm must not located on any physical xenserver hosts, but should stay on shared NFS share storage resource.
- my xenserver host1 has 4 NIC, setting default vm on host1 has 4 NIC while my xenserver host2 has only 2 NIC. Thus, seeing error "cannot see network" because host2 only have 2 NIC thus any vm on host2 can only have 2 NIC. => insight/solution: delete extra unneeded NIC on vm, left 1-2, then problem solve. vm has same number of NICs, which are supported in either xenserver hosts.
- vm must have xen tools installed - else menu live migration won't exist.

Summary:
- set up NFS is tricky, take long time 4-5 hours but it must be done else nothing work
- some pitfalls in configuring vm for live migrations to watch out ( take another 4-5 hours)

total 1-2 full works day to configure live migration. End of day experience of working live migration is sweet and so well worth it.