My Cache or Yours? Making Storage More Exclusive
My Cache or Yours? Making Storage More Exclusive
复制标题
DOI：
10.21236/ada396854
复制
发表时间：
2002-06
期刊：
影响因子：
--
通讯作者：
T. Wong;J. Wilkes
中科院分区：
文献类型：
--
作者：
T. Wong;J. Wilkes
现代高端磁盘阵列通常具有几千兆字节的高速缓存RAM。遗憾的是，大多数阵列缓存使用在缓存层次结构的客户端级和阵列级复制相同数据块的管理策略：它们是包容性的。因此，聚合缓存的行为就像它只与客户端和数组缓存中较大的一个一样大，而不是两者的总和一样大。包容性是一种浪费：高速缓存RAM很昂贵。我们将探讨一种实现独占缓存的简单方案的好处，在该方案中，数据块缓存在客户端或磁盘阵列上，但不能同时缓存在客户端和磁盘阵列上。独占性有助于创造单个大型统一缓存的效果。我们引入降级操作来将从客户端弹出的数据传输到阵列，并通过仿真研究来探索其有效性。我们量化了跨合成工作负载和实际工作负载的降级的好处和管理费用。结果表明，我们可以获得有用的-有时是实质性的-加速比。在我们的研究中，我们还开发了一些新的缓存插入算法，这些算法显示了多客户端系统的前景，并报告了它们的一些性质。
Modern high-end disk arrays often have several gigabytes of cache RAM. Unfortunately, most array caches use management policies which duplicate the same data blocks at both the client and array levels of the cache hierarchy: they are inclusive. Thus, the aggregate cache behaves as if it was only as big as the larger of the client and array caches, instead of as large as the sum of the two. Inclusiveness is wasteful: cache RAM is expensive. We explore the benefits of a simple scheme to achieve exclusive caching, in which a data block is cached at either a client or the disk array, but not both. Exclusiveness helps to create the effect of a single, large unified cache. We introduce a DEMOTE operation to transfer data ejected from the client to the array, and explore its effectiveness with simulation studies. We quantify the benefits and overheads of demotions across both synthetic and real-life workloads. The results show that we can obtain useful—sometimes substantial—speedups. During our investigation, we also developed some new cache-insertion algorithms that show promise for multiclient systems, and report on some of their properties.