digraph G {
    node [ shape=box ]
    rankdir=LR;


    subgraph cluster_rz1 {

    VMs->{VMHost1,VMHost2,VMHostN}
    {VMHost1,VMHost2,VMHostN}->CephCluster;

    CephCluster->{Ceph1,Ceph2,CephN}

    }

    subgraph cluster_rz2 {

    VMs2->{VMHost21,VMHost22,VMHost2N}
    {VMHost21,VMHost22,VMHost2N}->CephCluster2;

    CephCluster2->{Ceph21,Ceph22,Ceph2N}

    }

    CephCluster->CephCluster2 [ label="Backup/Mirror" ];

}