论文标题
延迟的最佳存储和安排复制的片段，用于内存约束服务器
Latency optimal storage and scheduling of replicated fragments for memory-constrained servers
论文作者
论文摘要
我们考虑分布式存储系统的设置，其中单个文件被细分为相同大小的较小片段，然后用相同的高速缓存大小的服务器中的常见复制因子复制。传入的文件下载请求将发送给所有服务器，并且每当请求收集所有片段时，下载都会完成。在每个服务器上，我们有兴趣确定要存储的片段集，以及应访问片段的序列，以便将请求的平均文件下载时间最小化。我们将片段下载时间建模为一个指数随机变量独立变量，并且针对所有服务器的所有片段都相同分布，并证明平均文件下载时间可以根据所有不同片段下载的预期有用服务器的预期数量来降低限制。我们提出了确定性存储方案，该方案试图最大化有用的服务器数量。我们表明，找到访问片段的最佳顺序是马尔可夫决策问题，其复杂性随片段数量而成倍增长。我们提出了启发式算法，以确定对片段的访问顺序，这些片段在经验上表现出很好的表现。
We consider the setting of distributed storage system where a single file is subdivided into smaller fragments of same size which are then replicated with a common replication factor across servers of identical cache size. An incoming file download request is sent to all the servers, and the download is completed whenever request gathers all the fragments. At each server, we are interested in determining the set of fragments to be stored, and the sequence in which fragments should be accessed, such that the mean file download time for a request is minimized. We model the fragment download time as an exponential random variable independent and identically distributed for all fragments across all servers, and show that the mean file download time can be lower bounded in terms of the expected number of useful servers summed over all distinct fragment downloads. We present deterministic storage schemes that attempt to maximize the number of useful servers. We show that finding the optimal sequence of accessing the fragments is a Markov decision problem, whose complexity grows exponentially with the number of fragments. We propose heuristic algorithms that determine the sequence of access to the fragments which are empirically shown to perform well.
