MySQL Manual
4 Database Administration
- 4.10 Replication in MySQL
- 4.10.1 Introduction
- 4.10.2 Replication Implementation Overview
- 4.10.3 Replication Implementation Details
- 4.10.4 How To Set Up Replication
- 4.10.5 Replication Features and Known Problems
- 4.10.6 Replication Options in `my.cnf'
- 4.10.7 SQL Commands Related to Replication
- 4.10.8 Replication FAQ
- 4.10.9 Troubleshooting Replication
4.10.1 Introduction
One-way replication can be used is to increase both robustness and speed. For robustness you can have two systems and can switch to the backup if you have problems with the master. The extra speed is achieved by sending a part of the non-updating queries to the replica server. Of course this only works if non-updating queries dominate, but that is the normal case.
Starting in Version 3.23.15, MySQL supports one-way replication internally. One server acts as the master, while the other acts as the slave. Note that one server could play the roles of master in one pair and slave in the other. The master server keeps a binary log of updates (see section 4.9.4 The Binary Log) and an index file to binary logs to keep track of log rotation. The slave, upon connecting, informs the master where it left off since the last successfully propagated update, catches up on the updates, and then blocks and waits for the master to notify it of the new updates.
Note that if you are using replicating all updates to the tables you replicate should be done through the master, unless you are always careful of avoiding conflicts between updates which users issue on the master and those which users issue on the slave.
Another benefit of using replication is that one can get non-disturbing backups of the system by doing a backup on a slave instead of doing it on the master. See section 4.4.1 Database Backups.
