Efficient fine granularity multi-version file system

A snapshot-based fine granularity versioning technique is presented to retain history data only for a single directory or a single file, and bring flexibility to multi-version file systems. Adopting the strategy to search in name space and version space separately, this paper also presents backward inheriting path-finding mechanism in version space. This mechanism is beneficial to the performance and management, because it can utilize the coupling relationship between versions to optimize the data layout of versions and build hierarchy in version space to accelerate the path-finding procedure. In addition, fast index structures for directory versions and file versions are designed. This prototype file system--THVFS can achieve both good performance and high availability with these technologies mentioned above. The experimental results show that the average time of searching old versions in THVFS was reduced by 34.4% than in ext3cow, the famous multi-version file system. In the trace experiment, the average read response time in THVFS was 12% less than in ext3, and only 80% extra space was needed to retain all history data when snapshots are taken every 72 minutes in THVFS. © by Institute of Software, the Chinese Academy of Sciences. All rights reserved.