try to document disaster scenarios

service/crm.md

@@ -128,9 +128,11 @@ accessible only by TPA. To add a user, on the backend server
 
 ## Disaster recovery
 
-<!-- what to do if all goes to hell. e.g. restore from backups? -->
-<!-- rebuild from scratch? not necessarily those procedures (e.g. see -->
-<!-- "Installation" below but some pointers. -->
+If Redis dies, we might lose in-process donations. But otherwise, it
+is disposable and data should be recreated as needed.
+
+If the entire database gets destroyed, it needs to be restored from
+backups, by TPA.
 
 # Reference