Session Description: The talk wants explain the data replication framework and how it works (concepts, algorithms, advantages and disadvantage). In special way how we distribute the block data across the ring and the communication protocol for election and failure detection. Pisa is a decentralized block storage replication framework with the specific goal of simplifying the development of storage back-end services in a distributed environment. Main characteristics of the project are the message security, self-organization cluster and simple setup. Pisa is a subproject of RestFS project and the talk will explain our experience acquired with the development of this subcomponent and the decisions taken in the design of the framework. The talk will explain deeply the algorithms used for the data replication across the network in the PISA project like: - DHT used - Cluster election and Failure Detection - Error Detection - Failure recover