Responding to membership changes to a set of storage systems that are synchronously replicating a dataset

A cloud-based storage system in a cloud computing environment, the cloud-based storage system including:

• one or more cloud computing instances with local block storage;
• cloud-based object storage;
• and
• one or more storage controller applications, each storage controller application executing in a cloud computing instance, wherein the one or more storage controllers are configured to:
• detect a change in membership to a set of storage systems synchronously replicating a dataset;
• and
• for one or more I/O operations directed to the dataset, apply the one or more I/O operations to the dataset synchronously replicated by a new set of storage systems, wherein storage systems synchronously replicating the dataset are included in a membership data structure of in-sync members, and wherein in-sync members correspond to a management entity representing the dataset, a set of managed objects, and a set of management operations.