updates related to cassandra2

Filer-Cassandra-Setup.md

@@ -18,10 +18,11 @@ create keyspace seaweedfs WITH replication = {
 use seaweedfs;
 
 CREATE TABLE filemeta (
+  dirhash bigint,
   directory varchar,
   name varchar,
   meta blob,
-  PRIMARY KEY (directory, name)
+  PRIMARY KEY ((dirhash, directory), name)
 ) WITH CLUSTERING ORDER BY (name ASC);
 
 ```
@@ -33,7 +34,7 @@ Try run ```weed filer -h``` to see an example filer.toml file. The file should b
 Here is the shortest example for Cassandra
 
 ```bash
-[cassandra]
+[cassandra2]
 enabled = true
 keyspace="seaweedfs"
 hosts=[

Super-Large-Directories.md

@@ -61,7 +61,7 @@ The consequences are:
 In `filer.toml` for Cassandra/Redis, there is an option `superLargeDirectories`. For example, if you will have a lot of user data under `/home/users`
 
 ```
-[cassandra]
+[cassandra2]
 ...
 superLargeDirectories = [
   "/home/users",