학위논문(석사)--서울대학교 대학원 :공과대학 컴퓨터공학부,2019. 8. 엄현상.To meet the exascale I/O requirements in the High-Performance Computing (HPC), a new I/O subsystem, named Burst Buffer, based on non-volatile memory, has been developed. However, the diverse HPC workloads and the bursty I/O pattern cause severe data fragmentation to SSDs, which creates the need for expensive garbage collection (GC) and also increase the number of bytes actually written to SSD. The new multi-stream feature in SSDs offers an option to reduce the cost of garbage collection. In this paper, we leverage this multi-stream feature to group the I/O streams based on the user IDs and implement this strategy in a burst buffer we call BIOS, short for Burst Buffer with an I/O Separation scheme. Furthermore, to optimize the I/O separation scheme in burst buffer environments, we propose a stream-aware scheduling policy based on burst buffer pools in workload manager and implement the real burst buffer system, BIOS framework, by integrating the BIOS with workload manager. We evaluate the BIOS and framework with a burst buffer I/O traces from Cori Supercomputer including a diverse set of applications. We also disclose and analyze the benefits and limitations of using I/O separation scheme in HPC systems. Experimental results show that the BIOS could improve the performance by 1.44× on average and reduce the Write Amplification Factor (WAF) by up to 1.20×, and prove that the framework can keep on the benefits of the I/O separation scheme in the HPC environment.Abstract
Introduction 1
Background and Challenges 5
Burst Buffer 5
Write Amplification in SSDs 6
Multi-streamed SSD 7
Challenges of Multi-stream Feature in Burst Buffers 7
I/O Separation Scheme in Burst Buffer 10
Stream Allocation Criteria 10
Implementation 12
Limitations of User ID-based Stream Allocation 14
BIOS Framework 15
Support in Workload Manager 15
Burst Buffer Pools 16
Stream-Aware Scheduling Policy 18
Workflow of BIOS Framework 20
Evaluation 21
Experiment Setup 21
Evaluation with Synthetic Workload 21
Evaluation with HPC Applications 25
Evaluation with Emulated Workload 27
Evaluation with Different Striping Configuration 29
Evaluation on BIOS Framework 30
Summary and Lessons Learned 33
An I/O Separation Scheme in Burst Buffer 33
Evaluation with Synthetic Workload 33
Evaluation with HPC Applications 33
Evaluation with Emulated Workload 34
Evaluation with Striping Configurations 34
A BIOS Framework 34
Evaluation with Real Burst Buffer Environments 34
Discussion 36
Limited Number of Nodes 36
Advanced BIOS Framework 37
Related work 38
Conclusions 40
Bibliography 42
초록 48Maste
