UMR-EC: A Unified and Multi-Rail Erasure Coding Library for High-Performance Distributed Storage Systems

Distributed storage systems typically need data to be stored redundantly to guarantee data durability and reliability. While the conventional approach towards this objective is to store multiple replicas, today's unprecedented data growth rates encourage modern distributed storage systems to employ Erasure Coding (EC) techniques, which can achieve better storage efficiency. Various hardware-based EC schemes have been proposed in the community to leverage the advanced compute capabilities on modern data center and cloud environments. Currently, there is no unified and easy way for distributed storage systems to fully exploit multiple devices such as CPUs, GPUs, and network devices (i.e., multi-rail support) to perform EC operations in parallel; thus, leading to the under-utilization of the available compute power. In this paper, we first introduce an analytical model to analyze the design scope of efficient EC schemes in distributed storage systems. Guided by the performance model, we propose UMR-EC, a Unified and Multi-Rail Erasure Coding library that can fully exploit heterogeneous EC coders. Our proposed interface is complemented by asynchronous semantics with optimized metadata-free scheme and EC rate-aware task scheduling that can enable a highly-efficient I/O pipeline. To show the benefits and effectiveness of UMR-EC, we re-design HDFS 3.x write/read pipelines based on the guidelines observed in the proposed performance model. Our performance evaluations show that our proposed designs can outperform the write performance of replication schemes and the default HDFS EC coder by 3.7x - 6.1x and 2.4x - 3.3x, respectively, and can improve the performance of read with failure recoveries up to 5.1x compared with the default HDFS EC coder. Compared with the fastest available CPU coder (i.e., ISA-L), our proposed designs have an improvement of up to 66.0% and 19.4% for write and read with failure recoveries, respectively.