Thank you both Michel and Christian. Looks like I will have to do the rebalancing eventually. From past experience with Ceph 16 the rebalance will likely take at least a month with my 500 M objects. It seems like a good idea to upgrade to Ceph 17 first as Michel suggests. Unless: I was hoping that Ceph might have a way to reduce the rebalancing, given that all constraints about failure domains are already fulfilled. In particular, I was wondering whether I could play with the names of the "datacenter"s, to bring them in the same (alphabetical?) order as the hosts were so far. I suspect that this is what avoided the reshuffling on my my mini test cluster. I think it would be in alignment with Table 1 from the CRUSH paper: https://ceph.com/assets/pdfs/weil-crush-sc06.pdf E.g. perhaps take(root) select(1, row) select(3, cabinet) emit yields the same result as take(root) select(3, row) select(1, cabinet) emit ? Niklas