Before performing maintenance operations on a XenServer host that is part of
a resource pool, you should disable it (which prevents any VMs from being started on
it), then migrate its VMs to another XenServer host in the pool. This can most
readily be accomplished by placing the XenServer host into Maintenance mode
using XenCenter. See the XenCenter Help for details.
Placing the master host into maintenance mode will result in the loss of the
last 24hrs of RRD updates for offline VMs. This is because the backup
synchronization occurs every 24hrs.
Citrix highly recommends rebooting all XenServers prior to
installing an update and then verifying their configuration. This is because
some configuration changes only take effect when a XenServer is rebooted,
so the reboot may uncover configuration problems that would cause the update to