SANBoost: automated SAN-level caching in storage area network

The storage traffic for different logical units (LUs) of a disk array converge at the array's cache. The cache is allocated among the LUs approximately according to their relative I/O rates. In the case of nonuniform I/O rates and sensitivity to storage response times between differing applications in a storage area network (SAN), undesirable cache interference between LUs can result in unacceptable storage performance for some LUs. This paper describes SANBoost, a SAN-level caching approach that can be enabled selectively on a per-LU basis to provide a performance isolation mechanism for response time metrics related to storage quality of service (QoS). SANBoost automates hot data detection and migration processes in block-level storage. The design consists of a migration module implemented in a fabric-based SAN virtualization appliance and a solid-state disk (SSD) that acts as a cache resource within the same SAN. Simulation results quantify the impact of a specific static SANBoost caching policy on the SPC-1 benchmark workload and address the relative impact of adapting a threshold in the placement algorithm.