Towards A Unified Garbage Collection Strategy in ZNS Key-Value Store File Systems Using Same-Victim GC
Hamin Hwangbo, Joseph Ro, Sungjin Byeon, Safdar Jamil, Jun Young Han, Joo-Young Hwang, Youngjae Kim · 2024
Zoned Namespace (ZNS) SSDs are gaining traction for eliminating in-device GC and enabling application-aware data management. BlobDB, an enhanced RocksDB with key-value separation, reduces compaction overhead but suffers from the GC over GC (GoG) problem, causing redundant data copying during BlobDB’s GC and Zone Cleaning (ZC). To address this, this paper proposes Same-Victim GC, aligning the victims and sizes of both GCs. Specifically, we introduce the BlobDB-Aware Zone Allocation (BAZA) algorithm to allocate blob files by creation order, eliminate victim file mismatch between two GCs, and $Z_{-} C u t o f f$ to minimize BlobDB’s GC size without additional overhead. Implemented in ZenFS v2.14 and RocksDB v7.4, our solution eliminates valid data copying, doubles compaction performance, and improves space utilization by $1.28 \times$.