Client-side metadata prefetching is commonly used in wide area network (WAN) file systems because it can effectively hide network latency. However, most existing prefetching approaches do not meet the various prefetching requirements of multiple workloads. They are usually optimized for only one specific workload and have no or harmful effects on other workloads. In this paper, we present a new self-tuning client-side metadata prefetching scheme that uses two different prefetching strategies and dynamically adapts to workload changes. It uses a directory-directed prefetching strategy to prefetch the related file metadata in the same directory, and a correlation-directed prefetching strategy to prefetch the related file metadata accessed across directories. A novel self-tuning mechanism is proposed to efficiently convert the prefetching strategy between directory-directed and correlation-directed prefetching. Experimental results using real system traces show that the hit ratio of the client-side cache can be significantly improved by our self-tuning client-side prefetching. With regards to the multi-workload concurrency scenario, our approach improves the hit ratios for the no-prefetching, directory-directed prefetching, variant probability graph algorithm, variant apriori algorithm, and variant semantic distance algorithm by up to 15.22%, 6.32%, 10.08%, 11.65%, and 10.73%, corresponding to 25.24%, 18.11%, 23.53%, 24.94%, and 24.19% reductions in the average access time, respectively.

客户端元数据预取通常用于广域网（WAN）文件系统中，因为它可以有效地隐藏网络延迟。但是，大多数现有的预取方法无法满足多种工作负载的各种预取要求。它们通常仅针对一种特定的工作负载进行了优化，而对其他工作负载没有任何影响或没有有害影响。在本文中，我们提出了一种新的自调整客户端元数据预取方案，该方案使用两种不同的预取策略并动态地适应工作负载的变化。它使用目录定向的预取策略来预取同一目录中的相关文件元数据，并使用关联定向的预取策略来预取在目录中访问的相关文件元数据。提出了一种新颖的自调整机制，可以有效地在目录定向和相关定向的预取之间转换预取策略。使用实际系统跟踪的实验结果表明，通过我们自调整客户端的预取，可以大大提高客户端缓存的命中率。对于多工作负载并发方案，我们的方法将无预取，目录导向的预取，变体概率图算法，变体先验算法和变体语义距离算法的命中率提高了15.22％，6.32％，平均访问时间分别减少了10.08％，11.65％和10.73％，分别减少了25.24％，18.11％，23.53％，24.94％和24.19％。使用实际系统跟踪的实验结果表明，通过我们自调整客户端的预取，可以大大提高客户端缓存的命中率。对于多工作负载并发方案，我们的方法将无预取，目录导向的预取，变体概率图算法，变体先验算法和变体语义距离算法的命中率提高了15.22％，6.32％，平均访问时间分别减少了10.08％，11.65％和10.73％，分别减少了25.24％，18.11％，23.53％，24.94％和24.19％。使用实际系统跟踪的实验结果表明，通过我们自调整客户端的预取，可以大大提高客户端缓存的命中率。对于多工作负载并发方案，我们的方法将无预取，目录导向的预取，变体概率图算法，变体先验算法和变体语义距离算法的命中率提高了15.22％，6.32％，平均访问时间分别减少了10.08％，11.65％和10.73％，分别减少了25.24％，18.11％，23.53％，24.94％和24.19％。