[ceph-users] [multisite] The purpose of zonegroup

Hi folks, In the multisite environment, we can get one realm that contains multiple zonegroups, each in turn can have multiple zones. However, the purpose of zonegroup isn't clear to me. It seems that when a user is created, its metadata is synced to all zones within the same realm, regardless whether they are in different zonegroups or not. The same happens to buckets. Therefore, what is the purpose of having zonegroups? Wouldn't it be easier to just have realm and zones? Thanks,Yixin