Great God, I have some questions. According to mongodb official, when there are more than 2 nodes. It is recommended that the replica set has an odd number of members instead of arbitration.
This odd number of members refers toNumber of replica set initializations? After some nodes are hung upNumber of people participating in elections?
For example, I deploy a replica set with three members including a master and two secondary? If master is dead and there are still two secondary schools left, will these two secondary schools complete the election of a master?
If I don’t follow the official recommendation, I will deploy even numbers, 4 machines, 1 master and 3 secondary. After Master is hung up, won’t there be a master elected from the remaining three secondary schools?
I think that no matter how many planes you deploy (only discussing the situation where more than 2 need not be arbitrated), the most important thing is that after some members (regardless of master or secondary) hang up,The remaining machines that have not been hung up can be successfully elected, so it has little to do with how many machines are deployed.. Even if you initially deploy odd-numbered machines, if you hang up one, the remaining machines will be even-numbered.
Later, I read some articles on the internet, and this suggestion of odd number of nodes should only be meaningful when deployed across computer rooms, because if the two computers A,B, and 4 computers AB are evenly distributed, i.e. 2 computers on each side, when the network fails, the nodes in the AB meeting will hold their own elections at the same time? Because half of the four computers were not reached, the nodes in AB two computer rooms failed in the election (or the election would not take place). If there were five computers instead of four, then one of the computer rooms was three computers, reaching half, and the election was successful. Is this understanding correct?
Is there a great god who can give me an example? The relationship between the number of nodes in the same computer room and the success of the election?
Not only mongodb, you will find that almost all clusters with election function require an odd number of nodes. This is to prevent