How to do it...

1. Create three images in the ceph cluster as we did in the previous recipe:

       # rbd create image-1 --size 1024 --pool data 
         --image-feature exclusive-lock,journaling

1. Enable image mirroring on the data pool on the ceph and backup clusters:

        # rbd mirror pool enable data image

1. Add ceph cluster as a peer to backup cluster:

         root@ceph-node5 # rbd mirror pool peer add 
                           data client.local@ceph

1. Validate that peer is successfully added:

        # rbd mirror pool info

1. In the ceph cluster, enable image mirroring on image-1, image-2 and image-3 will not be mirrored:

        root@ceph-node1 # rbd mirror image enable data/image-1

1. Check mirror status in backup cluster to verify single image being mirrored:

          # rbd mirror pool status

1. Check the image status in the backup cluster to validate the statue of this image and that image being mirrored is image-1:

         # rbd mirror image status data/image-1