Ceph

Ceph has long allowed config options to be specified with spaces or underscores in ceph.conf, eg. mon target pg per osd and mon_target_pg_per_osd.

I have always favored using underscores - they make the option name clearly delimited, easier to cut/paste, and easier to grep for.

Mimic-style centralized config displays options with underscores,

src/common/options.cc uses underscores.

The only place we use spaces ... is documentation. eg. https://docs.ceph.com/en/latest/rados/configuration/osd-config-ref/#general-settings

So I propose that we wholesale update config option references throughout the doc tree. I'll volunteer to work on this, but @zdover23 I wanted to run it by you first.