Solution 1:

There was some controversy over this back in 2003 when Los Angeles Country asked manufactures/suppliers to stop using it.

This ultimately led different software platforms (like Drupal) to adopt, in 2014, the terms:

primary/replica

Other possible phrases that I like include:

  • parent/child
  • leader/follower

For more information: http://en.wikipedia.org/wiki/Master/slave_(technology)

Solution 2:

In technology, there's "controller/peripheral".