Performability Evaluation of Networked Storage Systems Using N-SPEK

This paper introduces a new benchmark tool for evaluating performance and availability (performability) of networked storage systems, specifically storage area network (SAN) that is intended for providing block-level data storage with high performance and availability. The new benchmark tool, named N-SPEK (Networked-Storage Performability Evaluation Kernel module), consists of a controller, several workers, one or more probers, and several fault injection modules. N-SPEK is highly accurate and efficient since it runs at kernel level and eliminates skews and overheads caused by file systems. It allows a SAN architect to generate configurable storage workloads to the SAN under test and to inject different faults into various SAN components such as network devices, storage devices, and controllers. Available performances under different workloads and failure conditions are dynamically collected and recorded in the N-SPEK over a spectrum of time. To demonstrate its functionality, we apply N-SPEK to evaluate the performability of a specific iSCSI-based SAN under Linux environment. Our experiments show that N-SPEK not only efficiently generates quantitative performability results but also reveals a few optimization opportunities for future iSCSI implementations.