CSAR: cluster storage with adaptive redundancy

Striped file systems such as the parallel virtual file system (PVFS) deliver high-bandwidth I/O to applications running on clusters. An open problem in the design of striped file systems is how to reduce their vulnerability to disk failures with the minimum performance penalty. We describe a novel data redundancy scheme designed specifically to address the performance issue. We demonstrate the new scheme within CSAR, a proof-of-concept implementation based on PVFS. By dynamically switching between RAID1 and RAID5 redundancy based on write size, CSAR consistently achieves the best of two worlds & RAID1 performance on small writes, and RAID5 efficiency on large writes. Using the popular parallel I/O benchmark BTIO, our scheme achieves 82% of the write bandwidth of the unmodified PVFS. We describe the issues in implementing our new scheme in a popular striped file system such as PVFS on a Linux cluster