(A) SAN-based high performance shared disk file system

Abstract

The performance of conventional distributed file systems is limited by the server computing power and network bandwidth. With the advent of Storage Area Network (SAN), disk data can be directly accessed via SAN while traditional central storage server services the disk data to other computers via network. SAN architecture is becoming popular and replacing the traditional storage architectures consisting of local storage network such as SCSI and IDE. The storage systems based on SAN are much different from conventional systems, and a new file system architecture is required for exploiting the performance benefit of SAN fully. In this dissertation, a SAN-based high performance shared disk file system, called SANfs, is proposed. Unlike traditional distributed file systems which are based on a centralized file server, SANfs is server-less; every host accesses the disks attached to SAN without depending on a centralized server. In designing our SANfs, we take three things into consideration; data consistency and metadata managements, data integrity using RAID-5, and directory acceleration for very large directories. To fully exploit the scalability of SAN-based storage architecture, the file system should provide efficient data consistency and metadata management methods. SANfs provides an efficient data consistency scheme based on a file level lease and a decentralized free block management scheme. The locking range of a lock is whole file blocks. Compared with block-level locking schemes, locking overhead is much reduced. The free block management is performed in a distributed way to reduce the load of the metadata server. The metadata such as inodes, inode maps, and block maps are separated from the storage area network to optimize SAN for bulk transfer. Since the number of disks is much larger and the mean-time-to-failure of disks is shorter than the traditional SCSI, data integrity is an important issue. In SANfs, software RAID-5 is supported to tolerate a sing...