A Fully Decentralized File System Cache for the CernVM-FS

Scientific computing often takes place on globally scattered resources. The CernVM web file system supports such scenarios. It was designed to easily retrieve files from the web server that provides the CERN software distributions. In this paper, we extend the CernVM file system. We propose a distributed algorithm to retrieve cached data from the memory of participating peers. Users at the same department shall thereby experience a greatly reduced access latency. Our system forms a cache layer on top of the read-only CernVM-FS. It is fully decentralized and resilient to node churn. It gathers and shares information about file presence in the local network. Each peer can independently decide how much load it is willing to take.