An SSD-HDD Integrated Storage Architecture for Write-Once-Read-Once Applications on Clusters

After investigating the data processing characteristics of several scientific applications in various disciplines from bioinformatics to geology, we discover that they share one common feature: raw data is written once onto a storage system and then it is read into memory once for analyzing, after which it will seldom be used in the future. Typically, these scientific applications are running on a cluster where the storage system of each node is composed of an array of hard disk drives (HDDs). Although HDDs are economical, they become increasingly incompetent to meet the high I/O performance requirements imposed by these applications. Flash memory based solid-state-drives (SSDs), on the other hand, can provide a high performance and energy-efficiency. Still, they are relatively expensive than HDDs. In this paper, we propose a cost-effective yet high-performance storage architecture called SOHO (SSD-Workshop-HDD-Warehouse) for these write-once-read-once scientific applications like seismic wave analysis. Its basic idea is to process raw data in the workshop (i.e., SSD), and then, the processed data is moved to the warehouse (i.e., HDD) later. Experiments using both real-world scientific applications and synthetic traces demonstrate that on average SOHO outperforms a pure HDD storage system in mean response time by 78.25%. Compared to a pure SSD system, it only degrades mean response time by less than 3.11%.