We stop short of rewriting all playbooks for Prometheus, and instead
add references to the task of adding playbooks for
everything (prometheus-alerts#16) where we found references to
nagios.

howto/raid.md

@@ -199,10 +199,11 @@ currently not in use:
 
 ## Pager playbook
 
-Nagios should be monitoring hardware RAID on servers that support
-it. This is normally auto-detected by Puppet (in the `raid`
-module/class) but grep around for `megaraid` otherwise. The `raid`
-module should have a good README file describing how it works.
+Prometheus should be monitoring hardware RAID on servers that support
+it. This is normally auto-detected by the Prometheus node exporter.
+
+NOTE: those instructions are out of date and need to be rewritten for
+Prometheus, see [tpo/tpa/prometheus-alerts#16](https://gitlab.torproject.org/tpo/tpa/prometheus-alerts/-/issues/16).
 
 ### Failed disk