Lifetime-Aware Zone Allocation for ZNS SSDS

초록

Solid-state drives (SSDs) are deployed in fog, edge, and cloud environments owing to their high performance and reliability, making their lifespan critical concerns. Zoned Namespace SSDs (ZNS SSDs) address garbage collection (GC) overhead caused by out-of-place updates in conventional SSDs, providing stable and high write performance. RocksDB/ZenFS is a prominent system that leverages ZNS SSDs, where RocksDB, an LSM-tree-based key-value store, utilizes ZNS SSDs as storage through the ZenFS filesystem. To fully exploit RocksDB's write performance, multiple compaction threads are typically utilized. However, the existing zone allocation scheme in ZenFS often leads to high write amplification and frequent zone finish operations in multi-threaded compaction environments, thereby shortening the lifespan of ZNS SSDs. To address this issue, we propose Lifetime Ratio-based Zone Allocation (LRZA), a zone allocation scheme that considers the lifetime ratios of files grouped within a zone. LRZA eliminates the need for zone finish operations during allocation and effectively reduces write amplification caused by garbage collection. Experimental results demonstrate that LRZA reduces the number of used zones and zone reset operations by 10% and 14%, respectively, compared to ZenFS. These improvements contribute to extending the operational lifespan of ZNS SSDs while maintaining efficient write performance.

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