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《Journal of Systems Architecture》2014,60(8):684-692
Transaction support for filesystems has become a common feature in modern operating systems where data atomicity is achieved by writing transactions to the log region in advance. The logging mechanism is appropriate for flash storage devices due to the inherent nature of flash memory. However, the logging schemes inherently create multiple copies of data, leading to a decrease in the bandwidth of storage systems. In this paper, we present a simple and efficient invalidation scheme for multiple copies of data in a common journaling module. We identify two types of duplications, one in which there is an explicit duplication of the journal region and original region with the same data, and the other in which there is an implicit duplication of transaction commit operations. The invalidation of duplicated data reduces internal write and erase operations and garbage collection overhead for flash devices, which would otherwise increases external I/O bandwidth. Experimental results show that the overall performance improves roughly from 5% to 35% with the invalidation scheme for journal transactions. 相似文献
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Legacy system migration to the cloud brings both great challenges and benefits, so there exist various academic research and industrial applications on legacy system migration to the cloud. By analyzing the research achievements and application status,we divide the existing migration methods into three strategies according to the cloud service models integrally. Different processes need to be considered for different migration strategies, and different tasks will be involved accordingly. The similarities and differences between the migration strategies are discussed, and the challenges and future work about legacy system migration to the cloud are proposed. The aim of this paper is to provide an overall presentation for legacy system migration to the cloud and identify important challenges and future research directions. 相似文献
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Soha S. Zaghloul Najlaa AHuwaishel Maram AlAlwan 《通讯和计算机》2014,(6):479-483
A multiprocessor envirorLment may encounter many problems such as deadlock, load balancing and cache coherence. However, the latter is considered the most dangerous if not properly designed, the system works naturally but generates inaccurate results. This occurs if obsolete versions of a memory block are used. Users may not be aware of the presence of such problem. Two main approaches are known to maintain data consistency: namely, snoopy and directory-based protocols. Each approach has its advantages and limitations. This paper proposes a new technique that considers both previously mentioned approaches. The network architecture is slightly updated by adding an index table to each processor. The proposed protocol is expected to reduce the access time, decrease the number of accesses to main memory, maintain data consistency, and assure the usage of the most recent value of a shared variable. 相似文献
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Klaus Trangbaek 《Asian journal of control》2014,16(1):40-49
This paper deals with system identification for control of linear parameter varying systems. In practical applications, it is often important to be able to identify small plant changes in an incremental manner without shutting down the system and/or disconnecting the controller; unfortunately, closed‐loop system identification is more difficult than open‐loop identification. In this paper we prove that the so‐called Hansen scheme, a technique known from linear time‐invariant systems theory for transforming closed‐loop system identification problems into open‐loop‐like problems, can be extended to accommodate linear parameter varying systems as well. We investigate the identified subsystem's parameter dependency and observe that, under mild assumptions, the identified subsystem is affine in the parameter vector. Various identification methods are compared in direct and Hansen Scheme setups in simulation studies, and the application of the Hansen Scheme is seen to improve the identification performance. 相似文献