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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: Zookeeper Cross Datacenter Cluster
Date Mon, 06 Mar 2017 22:43:53 GMT
Consider using 3 DCs, not 2. If you have 3 then you can stand to lose 1 of them. Think of each
data center as an instance in a quorum. Always use odd numbers when possible.

-JZ

> On Mar 6, 2017, at 2:42 PM, Le Cyberian <lecyberian@gmail.com> wrote:
> 
> Thank for your replies.
> 
> I see, in that way then failover won't be possible as if the main/major DC
> is down.
> 
> Is there something i can do using hierarchical quorum groups or observers ?
> 
> I am quiet confused to achieve this setup somehow, as how someone would
> build a failover over 2 dc's :-/
> 
> On Mon, Mar 6, 2017 at 11:08 PM, Van Klaveren, Brian N. <
> bvan@slac.stanford.edu> wrote:
> 
>> Or, an extra server in a third datacenter to break the tie.
>> 
>> Brian
>> 
>> 
>>> On Mar 6, 2017, at 2:05 PM, Jordan Zimmerman <jordan@jordanzimmerman.com>
>> wrote:
>>> 
>>> This scenario is not possible. An even number of servers doesn't help
>> you as a quorum in ZooKeeper is (N/2)+1. So, if you put 2 servers in each
>> DC, a network partition would disable BOTH DCs. (4/2)+1 == 3. So, the only
>> option is to choose one of the DCs as the main DC and put an extra server
>> there. This way you could lose the "minor" DC.
>>> 
>>> -Jordan
>>> 
>>>> On Mar 6, 2017, at 11:34 AM, Le Cyberian <lecyberian@gmail.com> wrote:
>>>> 
>>>> Hi Guys,
>>>> 
>>>> I would like to have Kafka Cluster which is dependent on Zookeeper like
>>>> many other great projects out their. Kafka would have 4 nodes as its
>>>> cluster since their having even number is not a problem because it does
>>>> leader election based its config it keeps in zookeeper.
>>>> 
>>>> My scenario is having two server rooms on different floors having fiber
>>>> connectivity with each other so network latency / lag is almost like a
>>>> local connection.
>>>> 
>>>> However, I would like to implement zookeeper cluster between both of
>> them
>>>> for auto-failover / redundancy purposes. So if one server room is down
>>>> other should work properly.
>>>> 
>>>> For example: on a 5 node zookeeper cluster distributed on both of the
>>>> server rooms with 3 in one and 2 in other would give me 2 node failure
>>>> tolerance, However if the server room which has 3 servers is down then
>>>> ensemble would be broken and split brain.
>>>> 
>>>> Can you please suggest how to achieve this to have failover / redundancy
>>>> between two server rooms or two locations lets say ?
>>>> 
>>>> Is it possible to run 3 node cluster in each server room and have some
>> sort
>>>> of master-master between them ?
>>>> 
>>>> Thank for your time and helping out in advance.
>>>> 
>>>> Kind regards,
>>>> 
>>>> Le
>>> 
>> 
>> 


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