Re: Directing particular query on another machine

[James Day]

This is normally done by your application code (PHP or whatever else you use). Generally you'd have a function you write which chooses the server to use, then you control the rules it uses to decide which server gets the query.

The PHP code for Mediawiki contains an example of how to do this. Wikipedia uses that to share load between five servers, with variables in a configuration file saying which databases use which servers. Splitting reads by database increases cache hit rates and total performance for the set of servers.