Just to reiterate what you've explained, my understanding is now that keep_wal_segments is a minimum setting when replication slots are used, and in the event communications are lost, the number may grow as the slave still needs them. The growth may be such that it could fill up a filesystem, so precautions should be made by monitoring or having a way to redirect those segments to another growth area. My original thinking this morning was more likely the keep_wal_segments settings was a maximum not a minimum. Thanks for clearing that up for me.