Before removing a XenServer host from a pool, ensure that you shut down
all the VMs running on that host. Otherwise, you may see a warning stating that
the host cannot be removed.
Do not eject a host from a resource pool if it contains
important data stored on its local disks. All of the data will be erased upon
ejection from the pool. If you wish to preserve this data, copy the VM to shared
storage on the pool first using XenCenter, or the xe vm-copy CLI command.
When a XenServer host containing locally stored VMs is ejected from a pool,
those VMs will still be present in the pool database and visible to the other
XenServer hosts. They will not start until the virtual disks associated with
them have been changed to point at shared storage which can be seen by other
XenServer hosts in the pool, or simply removed. It is for this reason that you
are strongly advised to move any local storage to shared storage upon joining a
pool, so that individual XenServer hosts can be ejected (or physically fail)
without loss of data.