Patch-Based Data Management for Dual-Copy Buffers in RAID-Enabled SSDs

While a dual-copy redundant array of independent disk (RAID) buffering can remove single point of failure in the buffer of RAID-enabled solid-state drives (SSDs), it loses a half of buffer space efficiency as a result. This article introduces a patch-based data management scheme for dual-copy buffers in RAID-enabled SSDs, for better improving buffer use efficiency. Different from conventional methods that caches data/parity chunks in the RAID buffer, it caches the modified portions of data chunks (called data patches) and then employs a cost-evaluation model to direct patch data replacement. Besides, in order to correctly respond to applications' read/write requests, we design the patch-based read/write mode by taking the original dirty data chunks and relevant up-to-date patches into account. Through a series of simulation tests on several realistic disk traces, we illustrate that patch-based data management can work for RAID-enabled SSDs to enhance buffer use efficiency, and then yield better I/O performance. Especially, our proposal can noticeably reduce the I/O latency by 39.1% and the number of block erases by 3.9% on average, in contrast to state-of-the-art approaches.