Setup and configuration of a Ceph S3/Swift multi-site gateway

The solution consists of two clusters with multiple zones: An advanced configuration comprises a zone group and several individual zones, each of which has one or more Ceph (radosgw) instances. Each zone is backed by its own Ceph storage cluster. Having multiple zones in a group provides disaster recovery in case one of them suffers a major failure. Starting with the Kraken version, each zone is active and can accept write operations.