Clarify Geo Object Storage possibilities in docs

doc/administration/geo/replication/object_storage.md

@@ -9,15 +9,19 @@ type: howto
 
 Geo can be used in combination with Object Storage (AWS S3, or other compatible object storage).
 
-The storage method for files is recorded in the database, and the database is replicated
-from the **primary** Geo site to the **secondary** Geo site, so the **secondary** Geo site
-must match the storage method of the **primary** Geo site.
-Therefore, if the **primary** Geo site uses object storage, the **secondary** Geo site must use it too.
-
 Currently, **secondary** sites can use either:
 
 - The same storage bucket as the **primary** site.
 - A replicated storage bucket.
+- Local storage, if the primary uses local storage.
+
+The storage method (local or object storage) for files is recorded in the database, and the database
+is replicated from the **primary** Geo site to the **secondary** Geo site.
+
+When accessing an uploaded object, we get its storage method (local or object storage) from the
+database, so the **secondary** Geo site must match the storage method of the **primary** Geo site.
+
+Therefore, if the **primary** Geo site uses object storage, the **secondary** Geo site must use it too.
 
 To have: