A Hybrid Access Model for Storage Area Networks

We present HSAN - a hybrid storage area network, which uses both in-band (like NFS [13]) and out-of-band virtualization (like SAN FS [10]) access models. HSAN uses hybrid servers that can serve as both metadata and NAS servers to intelligently decide the access model per each request, based on the characteristics of requested data. This is in contrast to existing efforts that merely provide concurrent support for both models and do not exploit model appropriateness for requested data. The HSAN hybrid model is implemented using low overhead cache-admission and cache-replacement schemes and aims to improve overall response times for a wide variety of workloads. Preliminary analysis of the hybrid model indicates performance improvements over both models.