PostgreSQL replication is all about writing data. Therefore, the way PostgreSQL writes a chunk of data internally is highly relevant and directly connected to replication and replication concepts. In this section, we will dig into writes.
One of the first things we want to take a look at in this chapter is the PostgreSQL disk layout. Knowing about the disk layout can be very helpful when inspecting an existing setup, and it can be helpful when designing an efficient, high-performance installation.
In contrast to other database systems, such as Oracle, PostgreSQL will always rely on a filesystem to store data. PostgreSQL does not use raw devices. The idea behind this is that if a filesystem developer has done their job well, there is no need to reimplement the filesystem functionality over and over again.