u s e s t h e p r i m a r y c o p y r e p l i c a t i o nAbstract technique [1, 26, 27]. In this method, client calls are directed to a single primary server, which communicatesThis paper describes the design and implementation of the with other backup servers and waits for them to respondHarp file system. Harp is a replicated Unix file system before replying to the client. The system masks failures byaccessible via the VFS interface. It provides highly availperforming a failover algorithm in which an inaccessibleable and reliable storage for files and guarantees that file server is removed from service. When a primary performsoperations are executed atomically in spite of concurrency an operation, it must inform enough backups to guaranteeand failures. It uses a novel variation of the primary copy that the effects of that operation will survive all subsequentreplication techniquethat provides good performance befailovers.cause it allows us to trade disk accesses for network comHarp is...