Check-In: In-Storage Checkpointing for Key-Value Store System Leveraging Flash-Based SSDs

Persistent key-value store supports journaling and checkpointing to maintain data consistency and to prevent data loss. However, conventional data consistency mechanisms are not suitable for efficient management of flash memories in SSDs due to that they write the same data twice and induce redundant flash operations. As a result, query processing is delayed by heavy traffics during checkpointing. The checkpointing accompanies many write operations by nature, and a write operation consumes severe time and energy in SSDs; worse, it can introduce the write amplification problem and shorten the lifetime of the flash memory. In this paper, we propose an in-storage checkpointing mechanism, named Check-In, based on the cooperation between the storage engine of a host and the flash translation layer (FTL) of an SSD. Compared to the existing mechanism, our proposed mechanism reduces the tail latency due to checkpointing by 92.1 % and reduces the number of duplicate writes by 94.3 %. Overall, the average throughput and latency are improved by 8.1 % and 10.2 %, respectively.