An embedable key-value store for fast storage devices

Parallax is an LSM-based persistent key-value store designed for flash storage devices (SSDs, NVMe). Parallax reduces I/O amplification and increases CPU efficiency using the following mechanism. It categorizes key-value (KV) pairs into three size-based categories: Small, Medium, and Large. Then it applies a different policy for each category. It stores Small KV pairs inside the LSM levels (as RocksDB). It always performs key-value separation for KV pairs (as BlobDB), writing them in a value log, and it uses a garbage collection (GC) mechanism for the value log. For medium KV pairs, it uses a hybrid policy: It performs KV separation up to the semi-last levels and then stores them in place to bulk-free space without using GC.