When and how much can MySQL replication improve the performance of my system?
MySQL replication is most beneficial for a system that processes frequent reads and infrequent writes. In theory, by using a single-master/multiple-slave setup, you can scale the system by adding more slaves until you either run out of network bandwidth, or your update load grows to the point that the master cannot handle it.To determine how many slaves you can use before the added benefits begin to level out, and how much you can improve performance of your site, you need to know your query patterns, and to determine empirically by benchmarking the relationship between the throughput for reads (reads per second, or reads) and for writes (writes) on a typical master and a typical slave. The example here shows a rather simplified calculation of what you can get with replication for a hypothetical system.Let’s say that system load consists of 10% writes and 90% reads, and we have determined by benchmarking that reads is 1200 – 2 × writes. In other words, the system can do 1,200 reads per
