format

Directories-and-Files.md

@@ -43,7 +43,7 @@ visit "http://localhost:8888/path/to/sources/"
 visit "http://localhost:8888/path/to/sources/?lastFileName=abc.txt&limit=50"
 ```
 
-#### Architecture
+## Architecture
 
 For file reads:
 1. Filer lookup metadata from Filer Store, which can be Cassandra/Mysql/Postgres/Redis/LevelDB.