Grid is a type of parallel and distributed systems that is designed to provide reliable access to data and computational resources in wide area networks. These resources are distributed in different geographical locations. Efficient data sharing in global networks is complicated by erratic node failure, unreliable network connectivity and limited bandwidth. Replication is a technique used in grid systems to improve the applications’ response time and to reduce the bandwidth consumption. In this paper, we present a survey on basic and new replication techniques that have been proposed by other researchers. After that, we have a full comparative study on these replication strategies.