PostgreSQL 10 High Performance - Third Edition

checkpoint_completion_target

This specifies the target of checkpoint completion as a fraction of total time between checkpoints. The default is 0.5. The max_wal_size is a soft limit for total WAL size, so the database will try not to exceed it, but is allowed to, so keep enough free space on the partition and monitor it; the default value of max_wal_size is 1 GB, so the database will start a checkpoint after writing 500 MB of WAL, depending on checkpoint_completion_target (the default is 0.5).

It's reasonable at that point to also increase checkpoint_competion_target to its practical maximum of 0.9. This gives maximum checkpoint spreading, which theoretically means the smoothest I/O, too. In some cases keeping the default of 0.5 will still ...