cleanup

README.md

@@ -46,6 +46,14 @@ Configuration lives in `config.json` and can be overridden with
 every available key). At minimum, point `discovery.range_start`/`range_end`
 at the IP range your nodes live on.
 
+Certificates are loaded once per process:
+restart the node after rotating them. To set a key to null through the
+environment, use `@none` (a plain `null` is read as a string).
+
+Replicated storage (the vault and its replicas) travels as one archive, so it
+is limited to 16 MiB per node, and to `gateway.max_payload_bytes` (4 MiB by
+default) when a replica is fetched through a gateway.
+
 ## Controlling a node (`colonyctl`)
 
 `colonyctl` talks to the local node over its control socket: