Abstract: Some examples described herein relate to identifying a backup cluster for data backup. In an example, a primary source node may provide hash values of data on the primary source node to a plurality of cluster management systems, wherein each cluster management system manages a respective cluster. In response, the primary source node may receive mapping information of nodes in the respective cluster from corresponding cluster management system. The mapping information of a given node may indicate an extent of a match between the hash values of data on the source node and hash values of data on the given node. Based on mapping information of nodes, the primary source node may identify a backup cluster for backing up data on the primary source node.