Maintaining Object Ordering in a Shared P2P Storage Environment

• Authors: Germano Caronni;Raphael Rom;Glenn Scott
• Venue: SISW '05 Proceedings of the Third IEEE International Security in Storage Workshop
• Year: 2005

To be considered a viable storage solution, modern peer-to-peer (P2P) storage systems must exhibit high availability and data persistence characteristics. In an attempt to provide these, most systems assume a continuously connected and available underlying communication infrastructure. This however is not warranted in any real large-scale distributed system, and thus needs to be addressed. Continuous update systems that allow updating data by multiple writers have harder problems to overcome since the ordering of updates needs to be maintained independently of connectivity conditions. In this paper we propose a solution for maintaining a global view of the ordering even when severe connectivity disruptions take place, allowing the system to continue functioning while connectivity is disrupted and to recover from the disruption smoothly when connectivity is restored. To this end, we introduce and discuss three new concepts to the realm of P2P storage systems: 1) The maintenance of additional state information to detect and trace object updates during partitioning, 2) the usage of active decentralized object replication through shadow roots, and 3) the deployment of cryptographic technologies to allow for the recovery of private state information.