DeltaNC: Efficient File Updates for Network-Coding-Based Cloud Storage Systems

In recent years, cloud storage systems have emerged as the primary solution for online storage and information sharing. Due to efficient storage and bandwidth utilization, the use of erasure codes and network coding is proven to effectively provide fault tolerance and fast content retrieval in cloud storage systems. In a nutshell, coded blocks are distributed among storage nodes, and file retrieval is accomplished by downloading sufficient coded blocks from any group of storage nodes. However, due to high correlation between coded blocks and the original file, even a single-byte update invalidates all coded blocks in the system. In this paper, we introduce DeltaNC, a new differential update algorithm that keeps all coded blocks in a network-coding-based cloud storage system synchronized by transmitting only the changes in the file. Our experimental results, from a trace-driven simulator, show that DeltaNC significantly reduces the bandwidth and CPU usage and its performance is comparable to that offered by the Diff program, the common tool for updating files.