LBICA：一种适用于I/O Cache结构的负载均衡器
LBICA: A Load Balancer for I/O Cache Architectures
摘要：
近年来，企业级固态硬盘（SSD）被用于高性能服务器的缓存层，以缩小处理单元和存储子系统之间日益增长的性能差距。基于SSD的I/O缓存通常在突发访问的工作负载中无效，其中缓存层本身由于大量访问而成为性能瓶颈。现有的I/O Cache体系结构主要关注最大化Cache命中率，而忽略了访问的平均排队时间。以前的研究建议在识别突发访问时绕过缓存。然而，这些方案不适用于一般的高速缓存配置，并且还导致突发访问的显著性能下降。本文提出了一种新的I/O Cache负载均衡方案（LBICA），该方案具有自适应写策略管理，以防止I/O Cache在突发访问中成为性能瓶颈。我们的建议，不像以前的计划，禁用I/O缓存或绕过请求到磁盘子系统中的突发访问，选择性地减少了等待访问的SSD队列中的数量和平衡的I/O缓存和磁盘子系统之间的负载，同时提供最大的性能。该方案的特点的工作负载的类型的基础上，在队列中的请求，并分配一个有效的缓存写策略。我们的目标是绕过1）磁盘子系统服务速度更快或2）不能与I/O缓存队列中的其他访问合并的访问。这样，磁盘层将响应选定的请求，从而防止I/O缓存过载。我们对物理系统的评估表明，LBICA减少了48%的I/O缓存上的负载，并提高了30%的突发工作负载的性能相比，最新的国家的最先进的负载均衡计划。
英文摘要：
In recent years, enterprise Solid-State Drives (SSDs) are used in the caching layer of high-performance servers to close the growing performance gap between processing units and storage subsystem. SSD-based I/O caching is typically not effective in workloads with burst accesses in which the caching layer itself becomes the performance bottleneck because of the large number of accesses. Existing I/O cache architectures mainly focus on maximizing the cache hit ratio while they neglect the average queue time of accesses. Previous studies suggested bypassing the cache when burst accesses are identified. These schemes, however, are not applicable to a general cache configuration and also result in significant performance degradation on burst accesses. In this paper, we propose a novel I/O cache load balancing scheme (LBICA) with adaptive write policy management to prevent the I/O cache from becoming performance bottleneck in burst accesses. Our proposal, unlike previous schemes, which disable the I/O cache or bypass the requests into the disk subsystem in burst accesses, selectively reduces the number of waiting accesses in the SSD queue and balances the load between the I/O cache and the disk subsystem while providing the maximum performance. The proposed scheme characterizes the workload based on the type of in-queue requests and assigns an effective cache write policy. We aim to bypass the accesses which 1) are served faster by the disk subsystem or 2) cannot be merged with other accesses in the I/O cache queue. Doing so, the selected requests are responded by the disk layer, preventing from overloading the I/O cache. Our evaluations on a physical system shows that LBICA reduces the load on the I/O cache by 48% and improves the performance of burst workloads by 30% compared to the latest state-of-the-art load balancing scheme.
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