The Resyncing Objects view in the vCenter UI reports that some objects are currently resyncing.

Two actions that would cause some objects to be currently resyncing are:

A change to the storage policy is applied to the objects. This action triggers a resynchronization of objects to make them compliant with the new policy settings, such as FTT, RAID level, stripe width, etc. The resynchronization process copies data from one host to another to create or update replicas or parity segments.

A host failure occurs in the cluster. This action causes some objects to become non-compliant with their storage policy, as they lose one or more replicas or parity segments due to the host failure. The resynchronization process rebuilds the missing components on other hosts in the cluster to restore compliance and availability.References: : VMware vSphere Storage Guide, page 129 : Monitor the Resynchronization Tasks in the vSAN Cluster 1 : VMware vSAN Specialist v2 Exam Preparation Guide, page 13