Enabling a deleted-key-value-aware garbage collection strategy for LSM-tree on OCSSD

In general, NAND flash operates with a write-once characteristic and commonly uses the out-of-place update strategy for data updates. As a result, data instances often undergo multiple duplications, posing challenges for achieving thorough erasure. This issue becomes more acute in LSM-tree applications, where user-deleted data might not be entirely removed for a long time due to the inherent characteristics of NAND flash. To tackle this challenge, this study introduces a deleted-key-value-aware garbage collection strategy tailored for handling deleted key-value data. This strategy is designed to ensure that data targeted for deletion by users can be entirely erased in a single step during the data recovery phase. By implementing this strategy, the study aims to enhance data security and integrity in systems utilizing NAND flash memory.