setting for keep_wal_segments with replication slots, postgresql 9.4

Hi all,

I've been reading section 25.2.6 Replication Slots in the docs, and I'm
just a little confused. This section clearly states that replication slots
automates the management of WAL slots so the master will not remove them
prior to receipt by all standbys. Then, the second paragraph begins "In
lieu of using replication slots... use keep_wal_segments". So, if I have a
primary-standby cluster using a replication slot, then what, if anything,
should keep_wal_segments be set to? Should I just comment it out?

Also, if the slot is managing the storage of WAL segments, then isn't there
a possibility of filling up a disk in the event of an outage? And would
keep_wal_segments prevent that? This whole section just seems to be a
little vague to me and like it wasn't updated cleanly since slots were
envisioned.

Maybe it's just too early in the morning for me :-)
Jay