Data Freshness in Leader-Based Replicated Storage
Data Freshness in Leader-Based Replicated Storage
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DOI：
10.1109/isit44484.2020.9174411
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Amir Behrouzi-Far;E. Soljanin;R. Yates
中科院分区：
文献类型：
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作者：
Amir Behrouzi-Far;E. Soljanin;R. Yates
基于leader的数据复制通过对leader节点的顺序写入提高了高可用性分布式存储系统的一致性。在leader提交写操作后，“follower”节点通过多播机制写入，并且只保证最终的一致性。以信息时代（AoI）作为新鲜度度量，我们描述了领导者的数量如何影响通过瞬时读取查询检索到的数据的新鲜度。特别是，我们推导了一个确定性模型的leader写入时间和一个概率模型的follower写入时间的读查询的平均年龄。我们得到了指数分布的追随者写作时间的平均年龄的封闭表达式。我们的数值结果表明，根据对两组节点的写入操作的相对速度，存在一个使检索数据的平均年龄最小的最优leader数量，并且该数量随着leader上写入的相对速度的增加而增加。
Leader-based data replication improves consistency in highly available distributed storage systems via sequential writes to the "leader" nodes. After a write has been committed by the leaders, "follower" nodes are written by a multicast mechanism and are only guaranteed to be eventually consistent. With Age of Information (AoI) as the freshness metric, we characterize how the number of leaders affects the freshness of the data retrieved by an instantaneous read query. In particular, we derive the average age of a read query for a deterministic model for the leader writing time and a probabilistic model for the follower writing time. We obtain a closed-form expression for the average age for exponentially distributed follower writing time. Our numerical results show that, depending on the relative speed of the write operation to the two groups of nodes, there exists an optimal number of leaders which minimizes the average age of the retrieved data, and that this number increases as the relative speed of writing on leaders increases.