Strong and efficient consistency with consistency-aware durability

Aishwarya Ganesan, Ramnatthan Alagappan, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau

Research output: Contribution to journalArticlepeer-review


We introduce consistency-aware durability or Cad, a new approach to durability in distributed storage that enables strong consistency while delivering high performance. We demonstrate the efficacy of this approach by designing cross-client monotonic reads, a novel and strong consistency property that provides monotonic reads across failures and sessions in leader-based systems; such a property can be particularly beneficial in geo-distributed and edge-computing scenarios. We build Orca, a modified version of ZooKeeper that implements Cad and cross-client monotonic reads. We experimentally show that Orca provides strong consistency while closely matching the performance of weakly consistent ZooKeeper. Compared to strongly consistent ZooKeeper, Orca provides significantly higher throughput (1.8-3.3×) and notably reduces latency, sometimes by an order of magnitude in geo-distributed settings. We also implement Cad in Redis and show that the performance benefits are similar to that of Cad's implementation in ZooKeeper.

Original languageEnglish (US)
Article number4
JournalACM Transactions on Storage
Issue number1
StatePublished - Jan 2021
Externally publishedYes


  • Consistency models
  • Durability
  • Persistence
  • Replication

ASJC Scopus subject areas

  • Hardware and Architecture


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