When StorageType isEStorageType::Cachethis will return true as long each payload ends up being stored in at least one of the cache backends. When StorageType isEStorageType::Persistentthis will only return true if each payload endd up being stored inallof the backends. This is because the cache backends are not considered essential and it is not the end of the world if a payload is missing but the persistent backends must be reliable.