A storage system switching mediators within a storage system synchronously replicating data, where the switching between mediators includes: determining, among one or more of the plurality of storage systems, a change in availability of a first mediator service, wherein one or more of the plurality of storage systems are configured to request mediation from the first mediator service; communicating, among the plurality of storage systems and responsive to determining the change in availability of the first mediator service, a second mediator service to use in response to a fault; and switching, in dependence upon the change in availability of the first mediator service, from the first mediator service to the second mediator service.