1. A method implemented in a storage system, wherein a primary index stored on each node of the storage system has backups on at least two consecutive successor nodes, and the method comprises: receiving node failure information from a node; detecting along a predecessor direction and a successor direction of a failure node indicated in the node failure information according to a pre-stored node sequence to determine a first effective predecessor node and a first effective successor node, and all failure nodes between the first effective predecessor node and the first effective successor node; instructing all effective nodes having local content registration index stored on the failure nodes and the first effective successor node to perform a primary index recovery process that recovers primary indexes of all of the failure nodes into the primary index of the first effective successor.