地理分布式数据存储系统中延迟最优无编码存储方案的存在性研究
On Existence of Latency Optimal Uncoded Storage Schemes in Geo-Distributed Data Storage Systems
AI总结：
本文研究地理分布式存储系统的延迟优化问题，给出了同时实现单节点最坏情况延迟和系统平均延迟最优的无编码存储方案存在的充要条件，并针对无最优无编码方案的场景提出高效二进制存储码。
摘要：
我们研究服务器（或称节点）网络中的地理分布式数据存储问题，节点间通过具有特定往返时间（RTT）的通信链路相互连接。每个节点为特定的客户端集合提供服务，客户端可请求分布式系统中存储的任意文件。若请求的文件在本地可用，父节点直接提供该文件；否则它会联系其他存有目标数据的节点以获取请求的文件。这种节点间通信会产生延迟，进而导致数据请求的服务存在一定时延。服务节点的最坏情况延迟与系统平均延迟是存储系统的重要性能指标，它们不仅取决于节点间的往返时间（RTT），还与数据在各节点间的存储方式有关。数据文件可以原始形式即无编码方式存放在节点中，也可以编码后存放。本文给出了同时在单节点最坏情况延迟和系统平均延迟两方面达到最优的无编码存储方案存在的充要条件。此外，针对最优无编码方案不存在的特定场景，本文提出了高效的二进制存储码。
英文摘要：
We consider the problem of geographically distributed data storage in a network of servers (or nodes) where the nodes are connected to each other via communication links having certain round-trip times (RTTs). Each node serves a specific set of clients, where a client can request for any of the files available in the distributed system. The parent node provides the requested file if available locally; else it contacts other nodes that have the data needed to retrieve the requested file. This inter-node communication incurs a delay resulting in a certain latency in servicing the data request. The worst-case latency incurred at a servicing node and the system average latency are important performance metrics of a storage system, which depend not only on inter-node RTTs, but also on how the data is stored across the nodes. Data files could be placed in the nodes as they are, i.e., in uncoded fashion, or can be coded and placed. This paper provides the necessary and sufficient conditions for the existence of uncoded storage schemes that are optimal in terms of both per-node worst-case latency and system average latency. In addition, the paper provides efficient binary storage codes for a specific case where optimal uncoded schemes do not exist.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
