A Unified Buffer Cache Architecture that Subsumes Journaling Functionality via Nonvolatile Memory

Journaling techniques are widely used in modern file systems as they provide high reliability and fast recovery from system failures. However, it reduces the performance benefit of buffer caching as journaling accounts for a bulk of the storage writes in real system environments. To relieve this problem, we present a novel buffer cache architecture that subsumes the functionality of caching and journaling by making use of nonvolatile memory such as PCM or STT-MRAM. Specifically, our buffer cache supports what we call the in-place commit scheme. This scheme avoids logging, but still provides the same journaling effect by simply altering the state of the cached block to frozen. As a frozen block still provides the functionality of a cache block, we show that in-place commit does not degrade cache performance. We implement our scheme on Linux 2.6.38 and measure the throughput and execution time of the scheme with various file I/O benchmarks. The results show that our scheme improves the throughput and execution time by 89% and 34% on average, respectively, compared to the existing Linux buffer cache with ext4 without any loss of reliability.