Understanding PostgreSQL WAL and optimizing it with a dedicated disk
If you manage a PostgreSQL database with heavy write activity, one of the most important components to understand is the Write-Ahead Log (WAL). WAL is the foundation of PostgreSQL’s durability and crash recovery as it records every change before it’s applied to the main data files. But because WAL writes are synchronous and frequent, they can also become a serious performance bottleneck when they share the same disk with regular data I/O.