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arXiv · 2502.08982

Outback: Fast and Communication-efficient Index for Key-Value Store on Disaggregated Memory

Yi Liu·Minghao Xie·Shouqian Shi·Yuanchao Xu·Heiner Litz·Chen Qian
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Abstract

Disaggregated memory systems achieve resource utilization efficiency and system scalability by distributing computation and memory resources into distinct pools of nodes. RDMA is an attractive solution to support high-throughput communication between different disaggregated resource pools. However, existing RDMA solutions face a dilemma: one-sided RDMA completely bypasses computation at memory nodes, but its communication takes multiple round trips; two-sided RDMA achieves one-round-trip communication but requires non-trivial computation for index lookups at memory nodes, which violates the principle of disaggregated memory. This work presents Outback, a novel indexing solution for key-value stores with a one-round-trip RDMA-based network that does not incur computation-heavy tasks at memory nodes. Outback is the first to utilize dynamic minimal perfect hashing and separates its index into two components: one memory-efficient and compute-heavy component at compute nodes and the other memory-heavy and compute-efficient component at memory nodes. We implement a prototype of Outback and evaluate its performance in a public cloud. The experimental results show that Outback achieves higher throughput than both the state-of-the-art one-sided RDMA and two-sided RDMA-based in-memory KVS by 1.06-5.03x, due to the unique strength of applying a separated perfect hashing index.

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Yi Liu, Minghao Xie, Shouqian Shi, Yuanchao Xu, Heiner Litz, Chen Qian. 2025-02-13. Outback: Fast and Communication-efficient Index for Key-Value Store on Disaggregated Memory. https://doi.org/10.14778/3705829.3705849

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