United-FS: A Logical File System Providing a Single Image of Multiple Physical File Systems on NFS Server

NFS is considered to be the bottleneck in cluster computing environment because of its limited resources and centralized data management. With the development of hardware, NFS server has more than one I/O channel, more storage space and more powerful CPU. In this paper, we describe the design and the implementation of a new logical file system called United-FS. It can make storage devices connected to multiple I/O channels work concurrently and cooperatively. It can be exported by NFS server to provide a single file system image to clients by hiding a variety of native file systems built on different type of storage devices. This paper also compares the United-FS with the software RAID system both from theoretical analysis and experiments. The results show that United-FS is much more flexible and its performance is better than software RAID in most cases.