Fog Computing has emerged as a virtual platform extending Cloud services down to the network edge especially (and not exclusively) to host IoT applications. Data replication strategies have been designed to investigate the best storage location of data copies in geo-distributed storage systems in order to reduce its access time for different consumer services spread over the infrastructure. Unfortunately, due to the geographical distance between Fog nodes, misplacing data in such an infrastructure may generate high latencies when accessing or synchronizing replicas, thus degrading the Quality of Service (QoS). In this paper, we present two strategies to manage IoT data replication and consistency in Fog infrastructures. Our strategies choose for each datum, the right replica number and their location in order to reduce data access latency and replicas synchronization cost. This is done while respecting the required consistency level. Also, we propose an evaluation platform based on the simulator iFogSim to enable users to implement and test their own strategies for IoT data replication and consistency management. Our experiments show that when using our strategies, the service latency can be reduced by 30% in case of small Fog infrastructures and by 13% in case of large scale Fog infrastructures compared to iFogStor, a state-of-the-art strategy that does not use replication.

雾计算已成为将云服务扩展到网络边缘的虚拟平台，特别是（而不是专门）托管物联网应用程序。数据复制策略旨在研究地理分布式存储系统中数据副本的最佳存储位置，以减少其对分布在基础设施上的不同消费者服务的访问时间。不幸的是，由于 Fog 节点之间的地理距离，在这种基础设施中错放数据可能会在访问或同步副本时产生高延迟，从而降低服务质量 (QoS)。在本文中，我们提出了两种管理雾基础设施中物联网数据复制和一致性的策略。我们的策略为每个数据选择，正确的副本号及其位置，以减少数据访问延迟和副本同步成本。这是在遵守所需的一致性级别的同时完成的。此外，我们提出了一个基于模拟器的评估平台iFogSim使用户能够实施和测试他们自己的物联网数据复制和一致性管理策略。我们的实验表明，当使用我们的策略时，与iFogStor相比，在小型雾基础设施的情况下，服务延迟可以减少 30%，在大规模雾基础设施的情况下，服务延迟可以减少 13% ，这是一种最先进的策略，不使用复制。