ZNSwap: un-Block your Swap

Shai Bergman, Niklas Cassel, Matias Bjørling, Mark Silberstein

Research output: Contribution to journalArticlepeer-review


We introduce ZNSwap , a novel swap subsystem optimized for the recent Zoned Namespace (ZNS) SSDs. ZNSwap leverages ZNS's explicit control over data management on the drive and introduces a space-efficient host-side Garbage Collector (GC) for swap storage co-designed with the OS swap logic. ZNSwap enables cross-layer optimizations, such as direct access to the in-kernel swap usage statistics by the GC to enable fine-grain swap storage management, and correct accounting of the GC bandwidth usage in the OS resource isolation mechanisms to improve performance isolation in multi-tenant environments. We evaluate ZNSwap using standard Linux swap benchmarks and two production key-value stores. ZNSwap shows significant performance benefits over the Linux swap on traditional SSDs, such as stable throughput for different memory access patterns, and 10× lower 99th percentile latency and 5× higher throughput for memcached key-value store under realistic usage scenarios.

Original languageEnglish
Article number12
Pages (from-to)12:1-12:25
Number of pages25
JournalACM Transactions on Storage
Issue number2
StatePublished - 6 Mar 2023


  • SSD
  • Swap
  • ZNS

All Science Journal Classification (ASJC) codes

  • Hardware and Architecture


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