Eviction-based Cache Placement for Storage Caches

Most previous work on buffer cache management uses an access-based placement policy that places a data block into a buffer cache at the block’s access time. This paper presents an eviction-based placement policy for a storage cache that usually sits in the lower level of a multi-level buffer cache hierarchy and thereby has different access patterns from upper levels. The main idea of the eviction-based placement policy is to delay a block’s placement in the cache until it is evicted from the upper level. This paper also presents a method of using a client content tracking table to obtain eviction information from client buffer caches, which can avoid modifying client application source code. We have evaluated the performance of this eviction-based placement by using both simulations with real-world workloads, and implementations on a storage system connected to a Microsoft SQL server database. Our simulation results show that the eviction-based cache placement has an up to 500% improvement on cache hit ratios over the commonly used access-based placement policy. Our evaluation results using OLTP workloads have demonstrated that the eviction-based cache placement has a speedup of 1.2 on OLTP transaction rates.