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MQSim-E: Design and Implementation of an NVMe SSD Simulator for Enterprise SSDs
Duwon Hong, Dusol Lee, Jihong Kim
http://doi.org/10.5626/JOK.2022.49.4.271
In the study of storage systems such as SSD, a simulator that accurately mimic the operation of SW/HW inside the system plays an important role. In this paper, MQSim, which is widely used in research on NVMe SSDs, was shown to be inappropriate for the development of enterprise-SSD, and we propose an MQSim-E simulator that supports optimized techniques adopted in enterprise-SSD. MQSim-E fully utilizes the parallelism of flash memory and minimizes the performance overhead of garbage collection, improving IOPS, which is an important design goal for enterprise-SSDs, by up to 210% and reducing tail latency by up to 16,000% compared to the existing simulator (MQSim) to accurately reflect the characteristics of commercial enterprise SSDs.
Improving Performance of Flash Storage Using Restricted Copyback
Duwon Hong, Seulgi Shin, Jihong Kim
http://doi.org/10.5626/JOK.2019.46.8.726
In case of modern flash-based SSDs, the performance overhead of internal data migrations is dominated by the data transfer time and not by the flash program time as in old SSDs. In order to mitigate the performance impact of data migrations, we propose rcopyback, a restricted version of copyback. Rcopyback works in a manner similar to the original copyback except that only n consecutive copybacks are allowed. By limiting the number of successive copybacks, the version guarantees internal migration of data using rcopyback without any reliability problem. In order to take a full advantage of rcopyback, we developed a rcopyback-aware FTL, rcFTL, which intelligently decides whether rcopyback should be used or not by exploiting varying host workloads. Our evaluation results show that rcFTL can improve the overall I/O throughput by 54% on average over an existing FTL which does not use copybacks.
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