Also, slavery isn't a very good metaphor in many situations. If you have a DB "slave", the "master" really doesn't control it. The master doesn't enforce it's

Also, slavery isn't a very good metaphor in many situations. If you have a DB "slave", the "master" really doesn't control it. The master doesn't enforce it's functionality. The master won't typically supervise it, the master doesn't own it. The master didn't buy it, and there's really no economics in the situation at all. When you view systems in terms of autonomy and commitments (ie, promise theory), the metaphor of slavery becomes grossly inaccurate when trying to describe what a system is really doing. I'd call it a replica instead.