ELI5: How it works, etc. really works and what is a consensus algorithm

Question

It's hard for me to grasp what etcd really does (on CoreOS), because all of these "distributed key stores" seem intangible to me. Further reading, etc., It delves into Raft's consensus algorithm, and then becomes really confusing to understand.

Say what happens if the cluster system does not have etcd?

Thank you for your time and effort!

Answer 1

As a person with no CoreOS experience building a distributed system using etcd, I think I can shed some light on this.

etcd , , . , . , ; 5 , . , .

. , , . , 100% , , , , . - , . Paxos , . , . , , .

, etcd CoreOS, . , , , etcd. , , node ( ) , etcd ( ).

etcd , , , :

• etcd node , .
• x > x/2 , .
• , (, - netsplit), , .

, , .

Answer 2

etcd - . .

Raft .. . :

:

• node
• ( node, )
• -

• etcd , , .

  : etcd Postgres, .

:

• , - -
• , .