I've honestly tried this left and right and still find that my mirror server, set up as a replication slave still lags behind. My app's user base keeps growing and now Ive reached the point where I can't keep "shutting down" to "resync" databases (not even on weekends).
Anyways, my question: Are there any plausible, affordable, alternatives to binlog replication? I have two servers so wouldn't consider buying a third for load balancing just yet, unless its the only option.
Cheers,
/mp
Your master executes in parallel and your slave executes in serial. If your master can process 1.5 hours of inserts/updates/executes in 1 real hour, your slave will fall behind.
If you can't find ways to improve the write performance on your slave (more memory, faster disks, remove unnecessary indexes), you've hit a limitation in your applications architecture. Eventually you will hit a point that you can't execute the changes in real time as fast as your master can execute them in parallel.
A lot of big sites shard their databases: consider splitting your master+slave into multiple master+slave clusters. Then split your customer base across these clusters. When a slave starts falling behind, it's time to add another cluster.
It's not cheap, but unless you can find a way to make binlog replication execute statements in parallel you probably won't find a better way of doing it.
Update (2017): MySQL now support parallel slave worker threads. There are still many variables that will cause a slave to fall behind, but slaves no longer need to write in serial order. Choosing to preserve the commit order of parallel slave threads is an important option to look at if the exact state of the slave at any point in time is critical.