Fault Tolerance in Parallel System Using Multiple Stacks

The project describes a technique to tolerate faults in large data structures hosted on distributed servers, based on the concept of fused backups. The prevalent solution to this problem is replication. To tolerate the faults (dead/unresponsive data structures) among the whole distinct data structures, replication requires replicas of each data structure, resulting in number of servers and the number of fault for additional backups. This project present a solution, referred to as fusion that uses a combination of erasure codes and selective replication to tolerate f crash faults using just additional fused backups. This project shows that the solution achieves savings in space over replication. Further, this work present a solution to tolerate Byzantine faults (malicious data structures), that requires only backups as compared to the 2nf backups required by replication. We ensure that the overhead for normal operation in fusion is only as much as the overhead for replication. Though recovery is costly in fusion, in a system with infrequent faults, the savings in space outweighs the cost of recovery. This project explores the theory of fused backups and provides a library of such backups for all the data structures in the Visual Studio Collection Framework. The experimental evaluation confirms that fused backups are space-efficient as compared to replication (approximately n times), while they cause very little overhead for updates.