I have heard this question quite often: “At busy times, our replicas start lagging quite frequently. We are using N schemas, so which performance boost could we expect from MySQL 5.6 parallel replication?” Here is a quick way to give you a rough estimate of the potential benefit.

General idea

In MySQL 5.6, parallelism is added at the schema level. So in theory, if you have N schemas and if you use N parallel threads, replication could be up to N times faster. This assumes at least 2 things:

• Replication throughput scales linearly with the number of parallel threads.
• Writes are evenly distributed across schemas.

Both assumptions are of course not realistic. But it is easy to know the distribution of writes, and that can already give you an idea about how much you could benefit from parallel replication.

Writes are stored in binary logs but it is much easier to work with the …