Remzi H. Arpaci-Dusseau, University of Wisconsin-Madison - December 2009

How will flash impact the next generation of parallel and distributed storage systems? One view is that the primary location for flash in future systems is on the client side and not in the servers, which will remain disk-based. With flash on the clients, and disks on the servers, the responsibilities and roles of storage are dramatically altered. First, flash can decouple workloads from both network and server-side disk performance limits by serving as a large read cache and write buffer. Second, because data may persist in client-side flash storage, redundancy must exist not only across server disks but also include client-side flash.  We call this arrangement, hierarchical redundancy.Finally, as performance solutions migrate more to the client, the storage server can apply more aggressive space-saving techniques.This project will investigate a hybrid flash/disk architecture called Hierarchically Redundant Decoupled Storage System (HaRD) that enables massive performance improvements as well as capacity savings within large-scale storage systems. HaRD promises to change the way we build future storage clusters.