Evaluation of SSD Allocation Capacity Optimization Method between Tiered Volume and SSD Cache in Tiered Storage System

Abstract

We propose an SSD (Solid State Drive) allocation capacity optimization method between tiered volume and SSD cache and evaluate the storage I/O (Input/Output) response time with this method. When a combination of the volume tiering and SSD cache methods was applied, the SSD allocation capacity between them was optimized by only trial and error. The proposed method dynamically optimizes the SSD allocation capacity between them by simulating allocating larger and smaller SSD capacity to the SSD cache and calculating rates of I/Os to SSD. We show the proposed method optimizes it regardless of I/O characteristics, SSD capacity, and initial SSD allocation capacity between them. It reduces the storage I/O response time by up to 39% compared to the combination method.