Cambio del Pool-Master ed "evacuate" delle VMs

I assume if you only have two hosts you are probably not running HA. If you are using HA this disable HA first.
xe pool-ha-disable

Next get your list of hosts, you need the uuid for the next part
xe host-list 

Next, I would prefer to move the pool master role
xe pool-designate-new-master host-uuid=<xxxx>

Then do what you suggested:

disable logins so new VM's can't start
xe host-disable host=yyyy (I think this one is hostname instead of uuid)

move VM's to the others servers
xe host-evacuate uuid=<xxxx>

xe host-shutdown host=yyyy (I think this one is hostname too)

Replace the DIMM. When you fire it back up the Pool Master will need moved back if you 
want to keep it on the system you shut down. Turn HA back on if you turned it off initially.

That's about it.....

Alan Lantz
SysAdmin
City of Rogers, AR