-Re: Q about majority voting, # of nodes, even node number
Cameron McKenzie 2014-01-16, 05:05
My understanding (which is admittedly limited):
There are 2 nodes left out of 3, so when both machines respond they will
get 2/3 of the vote, thus forming a majority. If you only had 2 machines in
your cluster for example, then if 1 died, then the others vote would only
make up 1/2 of the vote, which is not the majority, so you get no extra
redundancy in having 2 machines over having 1.
On Thu, Jan 16, 2014 at 3:59 PM, Otis Gospodnetic <
[EMAIL PROTECTED]> wrote:
> Somebody asked me recently and I "got stuck" trying to explain this.
> When people ask how many ZK nodes they should have a common answer is "odd
> number: 3 or 5 or ...", so ZK can do majority voting. Correct so far?
> Another reason is for HA - if one ZK node dies, there are still 2 of them
> left. And this is where I am missing something core - with just 2 nodes
> left, how can ZK do majority voting now?
> Performance Monitoring * Log Analytics * Search Analytics
> Solr & Elasticsearch Support * http://sematext.com/