kafka 0.8 producer throughput

[Jun Guo -X (jungu - CIIC at Cisco)]

According to Kafka official document, the producer throughput is about 50MB/S. 
But I do some test, the producer throughout is only about 2MB/S. The test 
environment is the same with document says. One producer, One broker, One 
Zookeeper are in independent machine. Message size is 100 bytes, batch size is 
200, flush interval is 600 messages. The test environment is the same, the 
configuration is the same. The why there is such big gap the my test result and 
the document says?