Every hour a server replicates SQL server data with some external web server. During this time, which takes about 2-5minutes, the database seriously slows down. Colleagues, which work with the front end applications of that on another terminal server, even regularly start complaining.

The databases are also synchroniously mirrored (via SQLServer mirroring, no replication) to a third server. Note that 99% of the data is replicated outgoing, so the server should rarely need to update its data.

As the (merge and transactional) replication tasks are not time-critical, I would like to reduce their priority or somehow slow them down, so they don't affect the database performance that much.

How would you implement that?