yes, I do this every 2 months for Red Hat Linux patches.  with the mirror monitor make sure transactions are caught up then do "iris stop <production> quietly".  backup server then becomes primary.  when patch is done on the former primary you do "iris start <production>" and it will become the backup.  then do "iris stop <production> quietly on the current primary and the previous primary and then become primary again.  then do "iris start <production>" on the original backup and it will become backup again.