David already replied but here are my 2 cents. This is called “churn” (it brings up 50 results in search). It’s where nodes leave and other join the network. It adds to security because all data stored with these nodes now move somewhere else. On the other hand it’s a risky thing because if too many nodes fail at once a group might go from 10 nodes to only 5. This is handled in this way:
- There’s no fixed quorum size to make a decision in a group. So no need to always have at least 8 nodes in a group to make a decision. If 4 of them drop in an instant, there’s still 4 nodes left and they can make a decision with 3/4 agree.
- Nodes have addresses in XOR. So “close” doesn’t mean a thing in geographic terms. Your close nodes are probably all over the world, making the chance smaller that 4 or 5 of them churn at the same time as a region in a country loses internet.
- Archive Nodes are implemented. So even if we have a major blackout the network could be booted from 0.
- Connections in SAFE are fast and “heart beat” signals are send all the time to see if a node is alive or not. So if 2 nodes drop from a table with 9 nodes, the group knows in an instant. If the group got too small they could merge with another group (Disjoint Groups) and my guess is that this will happen in under a second.
This is what’s written by the Lee Clagett as well and I really don’t understand what he is asking for here. Now I’m not an engineer or coder but this is what’s said:
This is not a solution to the fundamental churn and partition problem. A
[newer document][3] mentions group merging, but does not describe how
groups with different states will be resolved.
This is a comment about Disjoint Groups. It makes the assumption that 2 groups should have the same “state” and therefore consensus on data/decisions and more. This is fundamentally wrong IMO. The idea behind Disjoint Groups is that each group is responsible for a certain range in the address space. So if group A1 becomes too small and the same happens with group A2 than each group still has it’s own “state” about everything they’re responsible for. So group A1 still signs stuff with quorum and group A2 does the same. They can’t conflict because the group sign (quorum) of each group is “law” so to speak. And when they decide to merge they accept each others previous signs and decisions. So IMO the writer of the article doesn’t have a good understanding of DG and therefore the current focus of the devs. But he’s free to explain here in the forum if I missed something in his statements.