We introduce
consistency-aware durability
or C
ad
, 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 O
rca
, a modified version of ZooKeeper that implements C
ad
and cross-client monotonic reads. We experimentally show that O
rca
provides strong consistency while closely matching the performance of weakly consistent ZooKeeper. Compared to strongly consistent ZooKeeper, O
rca
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 C
ad
in Redis and show that the performance benefits are similar to that of C
ad
’s implementation in ZooKeeper.
Download Time Analysis for Distributed Storage Codes with Locality and Availability