Is the sql server replicated on the backup server or do you have it externally from the two boxes?
QueueMetrics stores users, agents and campaigns informations on SQL. If you are able to force the backup box to the same SQL the official box is using, you don't have to worry about this information.
The only think you have to do is to start the qloader thread on the backup box and to configure the asterisk dialpan accordingly to what's already done on the official one.
Regards,
Marco Signorini