Database Replication

Normally we have more read than write ratio. So the number of slave database is normally higher than master database

Advantages

• Better performance: distribute read and write, allows queries to be processed parallely
• Failover: if master dies, we promote a slave up to be master. There is no dataloss
• High availability: even if the database is offline, you can still access the data in other databases
  • If a slave is offline, a new slave will be launch up to replace unhealthy slave
  • If master is offline, a slave is promoted to become master and a new slave is launched to replace it.