To store and manage data efficiently is the critical issue which modern information infrastructures confront with. To accommodate the massive scale of data in the Internet environment, most common solutions utilize distributed file systems. However there still exist disadvantages preventing these systems from delivering satisfying performance. In this paper, we present a Name Node cluster file system based on HDFS, which is named Clover. This file system exploits two critical features: an improved 2PC protocol which ensures consistent metadata update on multiple metadata servers and a shared storage pool which provides robust persistent metadata storage and supports the operation of distributed transactions. Clover is compared with HDFS and its key virtues are shown. Further experimental results show our system can achieve better metadata expandability ranging from 10% to 90% by quantized metrics when each extra server is added, while preserving similar I/O performance.