AdaCache: A Disaggregated Cache System with Adaptive Block Size for Cloud Block Storage

TL;DR

AdaCache is a disaggregated cache system with adaptive block sizing that improves cloud block storage performance by optimizing cache utilization and reducing memory overhead through innovative allocation and replacement strategies.

Contribution

It introduces an adaptive cache block allocation scheme and a group-based cache organization to enhance cache efficiency for diverse cloud workloads.

Findings

Significantly improves I/O performance in cloud storage environments.

Reduces cache memory usage compared to traditional fixed-size cache systems.

Achieves higher cache hit ratios with adaptive and group-based strategies.

Abstract

NVMe SSD caching has demonstrated impressive capabilities in solving cloud block storage's I/O bottleneck and enhancing application performance in public, private, and hybrid cloud environments. However, traditional host-side caching solutions have several serious limitations. First, the cache cannot be shared across hosts, leading to low cache utilization. Second, the commonly-used fix-sized cache block allocation mechanism is unable to provide good cache performance with low memory overhead for diverse cloud workloads with vastly different I/O patterns. This paper presents AdaCache, a novel userspace disaggregated cache system that utilizes adaptive cache block allocation for cloud block storage. First, AdaCache proposes an innovative adaptive cache block allocation scheme that allocates cache blocks based on the request size to achieve both good cache performance and low memory overhead. Second, AdaCache proposes a group-based cache organization that stores cache blocks into groups to solve the fragmentation problem brought by variable-sized cache blocks. Third, AdaCache designs a two-level cache replacement policy that replaces cache blocks in both single blocks and groups to improve the hit ratio. Experimental results with real-world traces show that AdaCache can substantially improve I/O performance and reduce storage access caused by cache miss with a much lower memory usage compared to traditional fix-sized cache systems.