Emerging storage systems with new flash exhibit ultra-low latency (ULL) that can address performance disparities between DRAM and conventional solid state drives (SSDs) in the memory hierarchy. Considering the advanced low-latency characteristics, different types of I/O completion methods (polling/hybrid) and storage stack architecture (SPDK) are proposed. While these new techniques are expected to take costly software interventions off the critical path in ULL-applied systems, unfortunately no study exists to quantitatively analyze system-level characteristics and challenges of combining such newly-introduced techniques with real ULL SSDs. In this work, we comprehensively perform empirical evaluations with 800GB ULL SSD prototypes and characterize ULL behaviors by considering a wide range of I/O path parameters, such as different queues and access patterns. We then analyze the efficiencies and challenges of the polled-mode and hybrid polling I/O completion methods (added into Linux kernels 4.4 and 4.10, respectively) and compare them with the efficiencies of a conventional interrupt-based I/O path. In addition, we revisit the common expectations of SPDK by examining all the system resources and parameters. Finally, we demonstrate the challenges of ULL SSDs in a real SPDK-enabled server-client system. Based on the performance behaviors that this study uncovers, we also discuss several system implications, which are required to take a full advantage of ULL SSD in the future.
|Title of host publication||Proceedings of the 2019 IEEE International Symposium on Workload Characterization, IISWC 2019|
|Publisher||Institute of Electrical and Electronics Engineers Inc.|
|Number of pages||12|
|Publication status||Published - 2019 Nov|
|Event||15th IEEE International Symposium on Workload Characterization, IISWC 2019 - Orlando, United States|
Duration: 2019 Nov 3 → 2019 Nov 5
|Name||Proceedings of the 2019 IEEE International Symposium on Workload Characterization, IISWC 2019|
|Conference||15th IEEE International Symposium on Workload Characterization, IISWC 2019|
|Period||19/11/3 → 19/11/5|
Bibliographical noteFunding Information:
ACKNOWLEDGMENT This is a full version of a 5-page workshop paper . In this work, we completely revised all the previous evaluation results from scratch by updating Linux kernel, Z-SSD firmware and hardware testbeds with the latest software/hardware version. The authors thank Samsung for the engineering sample donations and technical support. This research is mainly supported by NRF 2016R1C1B2015312. This work is also supported in part by NRF2015M3C4A7065645, DOE DE-AC02-05CH 11231, NRF2017R1A4A1015498, and Samsung grant (G01190271). The authors also thank Omesh Tickoo, Prof. J. W. Lee (SNU) and, J. Hwang (Samsung) for shepherding this paper and cooperative collaborations.
All Science Journal Classification (ASJC) codes
- Computer Graphics and Computer-Aided Design
- Hardware and Architecture