Extending Database Cache Using SSDs

Abstract

Advancements in speed, volume, and reliability have made solid-state device (SSD) a premium enterprise resource. SSDs are placed between main memory and hard disk devices (HDDs) when compared in terms of speed and cost. SSDs offer latencies lower than hard disk drives but have higher costs. In this paper, we demonstrate how enterprise class data management solutions can effectively use SSDs to manage competing goals of higher throughput and low resource costs. We demonstrate that SSDs can be used as a secondary caching layer between main memory-based buffer cache and HDD-based page store to meet these goals. Intelligent meta-data management ensures most important data or ‘hot data’ resides in RAM, ‘warm data’ resides in SSDs, and ‘cold data’ resides in HDDs. Hotness is measured dynamic and based on access pattern; hence, it needs no user intervention. SAP’s relational database server: SAP Adaptive Server Enterprise (SAP ASE) implements these ideas in its feature named ‘non-volatile cache.’