Replication on dbs

When two or more copies of data are stored in different places, it's called data replication.

Data replication is used for a variety of reasons:

• To keep data safe (for example, if one copy is lost or damaged, the others can be used to recreate it)
• To help users access data faster (for example, if data is stored in multiple locations, users can access the copy that's closest to them)
• To help systems keep running even if part of it fails (for example, if one database server goes down, the others can keep working)

Replication can be a complex topic, but we'll try to make it simple. Here's what you need to know about replication in relational databases.

As we said, replication is the process of copying data from one database to another.

In general terms, the source database is called the "master", and the destination database is called the "slave".

Based on the infrastructure and the design of our system, we can have different approaches:

• master/slave: where the master sends "fresh" data to the slave, which usually is used as a read-only replica;
• master/master: where both are considered masters and both acts as read-write nodes. Obviously, in this case is critical the synchronization between the twos.

Speaking of relational databases, we know that information is organized in tables (here is the article on relational databases), and replication can happen based on rows (when a row is updated, then the replication occurs) or based on the executed statement (when something happens, the replication occurs).

Which approach and kind of replication you should use depend on your situation; it's important to evaluate the pros and cons before proceeding.

For the moment, I hope it is clearer what replication is and that it is a very important aspect when your infrastructure grows (or needs to grow).

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