The Exchange 2010 SP1 installation failed at installing mailbox role with the error "Couldn't resolve the user or group "domain.local/Microsoft Exchange Security Groups/Discovery Management." If the user or group is a foreign forest principal, you must have either a two-way trust or an outgoing trust."
This issue could be caused by the Discovery Search Mailbox, Delete "DiscoverySearchMailbox" mailbox.and try to install again. You can recreate the Discovery Search Mailbox after installing Exchange 2010 SP1.
Delete "DiscoverySearchMailbox" mailbox.and try to install again