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Optimizing storage performance in public cloud platforms

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第12期12卷 951-964页

作者： Jian-zong WANG Peter VARMAN chang-sheng xie School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Wuhan National Laboratory for Optoelectronics Wuhan 430074 China Department of Electrical and Computer Engineering Rice University Houston 77005 USA

Cloud computing is an elastic computing model where users can lease computing and storage resources on demand from a remote infrastructure. It is gaining popularity due to its low cost, high reliability, and wide availability. With the emergence of public cloud storage platforms like Amazon, Microsoft, and Google, individual applications and enterprise storage are being deployed on Clouds. However, a serious impediment to its wider deployment is the relative lack of effective data management services. Our experiments, as well as industry reports, have shown that the performance and service-level agreement (SLA) cannot be guaranteed when the data is served over public Clouds. The relatively slow access to persistent data and large variability in cloud storage I/O performance can significantly degrade the performance of data-intensive applications. This paper addresses the issue of I/O performance fluctuation over public cloud platforms and we propose a middleware called CloudMW between the Cloud storage and clients to provide the storage services with better performance and SLA satisfaction. Some technologies, including data virtualization, data chunking, caching, and replication, are integrated into CloudMW to achieve a more stable and predictable performance, and permit flexible sharing of storage among the virtual machines (VMs). Experimental results based on Amazon Web Services (AWS) show that CloudMW is able to improve the stability and help provide better SLAs and data sharing for cloud storage.

关键词： Cloud storage Performance fluctuation Middleware Service-level agreement

An efficient data layout scheme for better I/O balancing in RAID-6 storage systems

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Frontiers of Information Technology & Electronic Engineering 2015年第5期16卷 335-345页

作者： Ping xie Jian-zhong HUANG Er-wei DAI Qiang CAO chang-sheng xie Wuhan National Laboratory for Opto Electronics Huazhong University of Science & Technology Computer College Qinghai Normal University

Among redundant arrays of independent disks(RAID)-6 codes, maximum distance separable(MDS)based RAID-6 codes are popular because they have the optimal storage efficiency. Although vertical MDS codes exhibit better load balancing compared to horizontal MDS codes in partial stripes, an I/O unbalancing problem still exists in some vertical codes. To address this issue, we propose a novel efficient data layout, uniform P-code(UPC), to support highly balanced I/Os among P-coded disk arrays(i.e., PC). In UPC, the nonuniformly distributed information symbols in each parity chain of P-code are moved along their columns to other rows, thus enabling the parity chain to keep original parity relationships and tolerate double disk failures. The UPC scheme not only achieves optimal storage efficiency, computational complexity, and update complexity, but also supports better I/O balancing in the context of large-scale storage systems. We also conduct a performance study on reconstruction algorithms using an analytical model. Besides extensive theoretical analysis, comparative performance experiments are conducted by replaying real-world workloads under various configurations. Experimental results illustrate that our UPC scheme significantly outperforms the PC scheme in terms of average user response time. In particular, in the case of a 12-disk array, the UPC scheme can improve the access performance of the RAID-6 storage system by29.9% compared to the PC scheme.

关键词： RAID-6 Data availability High performance I/O balancing

A reliable power management scheme for consistent hashing based distributed key value storage systems

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Frontiers of Information Technology & Electronic Engineering 2016年第10期17卷 994-1007页

作者： Nan-nan ZHAO Ji-guang WAN Jun WANG chang-sheng xie Wuhan National Laboratory for Optoelectronics Wuhan 430074 China Department of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Department of Electrical Engineering and Computer Science University of Central Florida Orlando FL 32816 USA

Distributed key value storage systems are among the most important types of distributed storage systems currently deployed in data centers. Nowadays, enterprise data centers are facing growing pressure in reducing their power consumption. In this paper, we propose GreenCHT, a reliable power management scheme for consistent hashing based distributed key value storage systems. It consists of a multi-tier replication scheme, a reliable distributed log store, and a predictive power mode scheduler （PMS）. Instead of randomly placing replicas of each object on a number of nodes in the consistent hash ring, we arrange the replicas of objects on nonoverlapping tiers of nodes in the ring. This allows the system to fall in various power modes by powering down subsets of servers while not violating data availability. The predictive PMS predicts workloads and adapts to load fluctuation. It cooperates with the multi-tier replication strategy to provide power proportionality for the system. To ensure that the reliability of the system is maintained when replicas are powered down, we distribute the writes to standby replicas to active servers, which ensures failure tolerance of the system. GreenCHT is implemented based on Sheepdog, a distributed key value storage system that uses consistent hashing as an underlying distributed hash table. By replaying 12 typical real workload traces collected from Microsoft, the evaluation results show that GreenCHT can provide significant power savings while maintaining a desired performance. We observe that GreenCHT can reduce power consumption by up to 35%-61%.

关键词： Consistent hash table (CHT) Replication Power management Key value storage system Reliability

Static recrystallization behavior of SA508Gr.4N reactor pressure vessel steel during hot compressive deformation

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Journal of Iron and Steel Research International 2021年第5期28卷 604-612页

作者： Shi-bin Qiao Xi-kou He chang-sheng xie Zheng-dong Liu Institute for Special Steels Central Iron and Steel Research InstituteBeijing 100081China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

The two-pass isothermal hot compression method was used to study the effect of different thermal deformation conditions on static recrystallization behavior in Ni-Cr-Mo series SA508Gr.4N low alloy steel with interval holding time ranging from 1 to 300 s,temperature ranging from 950 to 1150℃,strain rate ranging from 0.01 to 1 s^(-1),true strains ranging from 0.1 to 0.2,and initial austenite grain size ranging from 175 to 552μ*** can be concluded that the static recrystallization volume fraction gradually increases with the increase in the deformation temperature,strain rate,strain and pass interval,and the decrease in the initial grain size,which is mainly due to the increase in the deformation energy storage and ***,strain-induced grain boundary migration is the nucleation mechanism for static recrystallization of SA508Gr.4N low alloy *** on the stress-strain curve,the predicted value obtained from the established static recrystallization kinetics model is in good consistence with the experimental value,and the static recrystallization thermal activation energy of SA508Gr.4N steel was calculated as 264,225.99 J/mol.

关键词： Nuclear reactor pressure vessel Two-pass isothermal thermal compression Static recrystallization Kinetics model

Metadynamic recrystallization behaviors of SA508Gr.4N reactor pressure vessel steel during hot compressive deformation

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Journal of Iron and Steel Research International 2021年第1期28卷 46-57页

作者： Shi-bin Qiao Zheng-dong Liu Xi-kou He chang-sheng xie Institute for Special Steels Central Iron and Steel Research InstituteBeijing 100081China Collaborative Innovation Centre of Steel Technology University of Science and Technology BeijingBeijing 100083China

The metadynamic recrystallization(MDRX)model is established,and the coefficients determined by multiple linear regression analysis are used to describe the microstructure evolution of SA508Gr.4N *** effects of compression temperature of 950–1150℃,strain rate of 0.001–0.1 s^(-1),pre-strain of 0.3–0.6,initial austenite grain size(IAGS)of 136–552 lm,and interval time of 1–300 s on the MDRX kinetics and microstructure evolution were analyzed,using twopass compression test method on Gleeble thermo-mechanical *** results show that MDRX kinetics and austenite grain size are strongly dependent on compression temperature and strain rate,MDRX volume fraction increases with increasing compression temperature and strain rate,and the grain size decreases with increasing strain rate and decreasing compression temperature,while less affected by the pre-strain and ***,the values predicted using MDRX model and the ones calculated from experiment are compared,and the results show that the proposed model can give a reasonable estimate of MDRX behavior for SA508Gr.4N steel.

关键词： SA508Gr.4N steel Metadynamic recrystallization Kinetic model Grain size model

Constitutive modeling and critical strain of dynamic recrystallization in SA508Gr.4N steel for advanced pressure vessel materials

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Journal of Iron and Steel Research International 2018年第11期25卷 1189-1197页

作者： Zhi-qiang Yang Zheng-dong Liu Xi-kou He Shi-bin Qiao chang-sheng xie Institute for Special Steels Central Iron and Steel Research Institute GroupBeijing 100081China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

Using a Gleeble-1500D thermal-mechanical simulator,the hot-deformation behavior and critical strain in the dynamic recrystallization of SA508Gr.4N steel were investigated by compression tests from 1050 to 1250℃ with strain rates from 0.001 to 0.1 s^-***-strain curves were fitted by a nonlinear fitting *** on these tests,the flow stress constitutive equations of the work-hardening dynamical recovery period and dynamical recrystallization period Were established for SA508Gr.4N *** stress-strain curves of SA508Gr.4N steel predicted by the established models are in a good agreement with the experimental *** of ln θ -ε and --(a)(lnθ)/(a)ε-ε (where θ is the work-hardening rate and ε is true strain)were plotted from experimental data.A critical strain (εc)and a peak strain (εp)of dynamic recrystallization were obtained and exhibited a linear relationship,i.e.,εc =0.386ε*** predicted model of εc could be described by the equation of εc=1.604×10^-3Z^0.127.

关键词： SA508Gr.4N steel Hot deformation Constitutive modeling Critical strain Dynamic recrystallization

Write-Optimized B^(+) Tree Index Technology for Persistent Memory

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Journal of Computer Science & Technology 2021年第5期36卷 1037-1050页

作者： Rui-Xiang Ma Fei Wu Bu-Rong Dong Meng Zhang Wei-Jun Li chang-sheng xie Wuhan National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430070China Key Laboratory of Information Storage System Ministry of Education of ChinaWuhan 430070China Engineering Research Center of Data Storage Systems and Technology Huazhong University of Science and Technology Wuhan 430070China School of Computer Science and Technology Huazhong University of Science and TechnologyWuhan 430070China Shenzhen DAPU Microelectronics Co. LtdShenzhen 518116China

Due to its low latency,byte-addressable,non-volatile,and high density,persistent memory(PM)is expected to be used to design a high-performance storage ***,PM also has disadvantages such as limited endurance,thereby proposing challenges to traditional index technologies such as B(+)tree.B(+)tree is originally designed for dynamic random access memory(DRAM)-based or disk-based systems and has a large write amplification *** high write amplification is detrimental to a PM-based *** paper proposes WO-tree,a write-optimized B(+)tree for ***-tree adopts an unordered write mechanism for the leaf nodes,and the unordered write mechanism can reduce a large number of write operations caused by maintaining the entry order in the leaf *** the leaf node is split,WO-tree performs the cache line flushing operation after all write operations are completed,which can reduce frequent data flushing ***-tree adopts a partial logging mechanism and it only writes the log for the leaf *** inner node recognizes the data inconsistency by the read operation and the data can be recovered using the leaf node information,thereby significantly reducing the logging ***,WO-tree adopts a lock-free search for inner nodes,which reduces the locking overhead for concurrency *** evaluate WO-tree using the Yahoo!Cloud Serving Benchmark(YCSB)*** with traditional B(+)tree,wB-tree,and Fast-Fair,the number of cache line flushes caused by WO-tree insertion operations is reduced by 84.7%,22.2%,and 30.8%,respectively,and the execution time is reduced by 84.3%,27.3%,and 44.7%,respectively.

关键词： persist memory B^(+)tree write amplication consistency YCSB(Yahoo!Cloud Serving Benchmark)

Strip-oriented asynchronous prefetching for parallel disk systems

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第11期13卷 799-815页

作者： Yang LIU Jian-zhong HUANG Xiao-dong SHI Qiang CAO chang-sheng xie Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Wuhan 430074 China School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China

Sequential prefetching schemes are widely employed in storage servers to mask disk latency and improve system throughput. However, existing schemes cannot benefit parallel disk systems as expected due to the fact that they ignore the distinct internal characteristics of the parallel disk system, in particular, data striping. Moreover, their aggressive prefetching pattern suffers from premature evictions and prolonged request latencies. In this paper, we propose a strip-oriented asynchronous prefetching (SoAP) technique, which is dedicated to the parallel disk system. It settles the above-mentioned problems by providing multiple novel features, e.g., enhanced prediction accuracy, adaptive prefetching strength, physical data layout awareness, and timely prefetching. To validate SoAP, we implement a prototype by modifying the software redundant arrays of inexpensive disks (RAID) under Linux. Experimental results demonstrate that SoAP can consistently offer improved average response time and throughput to the parallel disk system under non-random workloads compared with STEP, SP, ASP, and Linux-like SEQPs.

关键词： Parallel disk system Strip Sequential prefetching Asynchronous scheduling

Microstructure and impact toughness of 16MND5 reactor pressure vessel steel manufactured by electrical additive manufacturing

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Journal of Iron and Steel Research International 2020年第8期27卷 992-1004页

作者： Xi-kou He chang-sheng xie Li-jun Xiao Ying Luo Di Lu Zheng-dong Liu Xi-tao Wang Institute for Special Steels China Iron and Steel Research InstituteBeijing 100081China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610041SichuanChina Southern Additive Science and Technology Co. Ltd.Foshan 528225GuangdongChina

Electrical additive manufacturing can improve manufacturing efficiency and reduce the cost of 16MND5 reactor pres-sure vessel steel. Impact tests were conducted to compare the impact toughness of 16MND5 steels manufactured by the electrical additive manufacturing and conventional forging, respectively. It is found that the impact toughness of electrical additive manufacturing specimen was slightly higher than that of conventional forging specimen. The characterizations of microstructure show that there were large ferrites and carbides in electrical additive manufacturing specimen. The fracture mechanisms of electrical additive manufacturing specimen were that microvoids or microcracks were prone to nucleate at the large ferrite/bainite interface and large carbide/bainitic ferrite interface, where the stress concentration was high. In addi-tion, the block size and high-angle grain boundaries played a vital role in hindering crack propagation of electrical additive manufacturing specimen, helping to improve the impact energy and leading to a low ductile–brittle transition temperature. The results suggest that the electrical additive manufacturing technology was an effective method to enhance the impact toughness of 16MND5 steel.

关键词： Electrical additive manufacturing 16MND5 steel Impact toughness Fracture High-angle grain boundary