A Study on Checkpointing for Distributed Applications Using BlockchainBased Data Storage Blockchain and smart contract technologies are becoming increasingly common in various areas. In these days, some userside software saves information into blockchainbased storage so that they can ensure security, traceability, and fault tolerance of their data. We expect that in the near future, more applications will use blockchainbased storage for dependability. However, there are some inconvenient points in current blockchain technologies for common use. Especially, stale blocks lead an undesirable property of blockchains, that is, a checkpoint saved into a blockchain may be invalidated later. In this article we develop a simulator for obtaining some parameters toward constructing an analytical model by using the parameters obtained.

A Novel Exploration for Blockchain in Distributed File Storage Distributed file storage provides reliable access to data through redundancy spread on distributed nodes. Various application scenarios emerge, such as include data centers, storage in wireless networks and peertopeer storage systems. Storing data by using code, such as an erasure code, calls for less redundancy compared with simple replication in terms of reliability. Nevertheless, since data fragments are periodically replaced when some nodes fail, a key acute question is how to generate encoded data fragments in a distributed way when transferring as little data as possible over the network. For a coded system, a new node to repair from a node failure is to download subsets of data from some surviving nodes, reconstructs some lost coded blocks by using the downloaded fragments, and stores them at the new node. This procedure is not optimal. In this paper, we introduce blockchain to protect distributed data in terms of node failure and etc. We show that blockchain can significantly improve the integrity and credibility in distributed file storage systems. Furthermore, we harvest theory discovery of blockchain in distributed file storage system.