USENIX Association 11th USENIX Conference on File and Storage Technologies (FAST ’13) 73 Unioning of the Buffer Cache and Journaling Layers with Non-volatile Memory

Journaling techniques are widely used in modern file systems as they provide high reliability and fast recov-ery from system failures. However, it reduces the per-formance benefit of buffer caching as journaling ac-counts for a bulk of the storage writes in real system environments. In this paper, we present a novel buffer cache architecture that subsumes the functionality of caching and journaling by making use of non-volatile 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 per-forms the function of caching, we show that in-place commit does not degrade cache performance. We im-plement our scheme on Linux 2.6.38 and measure the throughput and execution time of the scheme with vari-ous file I/O benchmarks. The results show that our scheme improves I/O performance by 76 % on average and up to 240 % compared to the existing Linux buffer cache with ext4 without any loss of reliability. 1