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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: Leader elections between 2 nodes.
Date Wed, 09 May 2018 15:29:58 GMT
A quorum means (n/2)+1 - In a 3 node cluster that is 2. So, if 2 servers are up you can achieve
quorum. 

> we need odd
> numbers in order to form a quorum

The "odd" in this formula refers to the number of configured servers not how many are running
at a given time. That's the reasoning for quorum in the first place. Quorum I/O ensures that
a majority of nodes is referenced for reads or writes (in ZooKeeper writes are what matter
for quorum). 

-Jordan

> On May 9, 2018, at 10:26 AM, Kaushal Shriyan <kaushalshriyan@gmail.com> wrote:
> 
> Hi,
> 
> In a ensemble of 3 nodes with 1 leader and 2 followers, if the leader goes
> down then two servers can elect a leader among themselves. But we need odd
> numbers in order to form a quorum. I am confused. Please correct me if i am
> understanding it wrong.
> 
> Any help will be highly appreciable
> 
> Best Regards,
> 
> Kaushal


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