Checkpoint: How often does Postgres save your data in case of catastrophic failure. Save too frequently increase CPU and IO load. And we can control how often Postgres does a checkpoint.
TODO: How to calculate your WAL quota?
TODO: How many checkpoints per hour?
First we need to look at how PostgreSQL write data.
INSERT INTO table(column) VALUES (value) ;
The value will be sent to WAL first. Then PostgreSQL will take it to Shared Buffer. BgWriter come to take the value, and write to correspondent location.
Because PostgreSQL could crash any time.