Managing reservations for at least two different sites competing for a resource includes maintaining a table of groups of sites, where each group competes for the same resource, one of the different sites requesting a reservation for a particular resource, determining if the reservation is available by consulting the table, denying the reservation to the one of the at least two different sites in response to access having been previously reserved for an other one of the different sites, and granting the reservation to the one of the at least two different sites and reserving access for the one of the at least two different sites in response to the resource being available. The managed resources may correspond to data storage and the two different sites may be mirrored storage devices. In response to a failure of communication between the two different sites, pending writes may be failed.