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From Michael Han <h...@cloudera.com>
Subject Re: Zookeeper in two data centers and disaster recovery
Date Fri, 09 Dec 2016 01:05:05 GMT
If "keep running" is defined as serving both read and write requests then
no there is no way to build a reliable ZooKeeper ensemble across only two
data centers simply because we can't guarantee that the single data center
remaining after another one is lost contains the majority number of servers
that can form a quorum. In this case you need at least 3 DC. If "keep
running" is defined as serving only read requests then you could enable
read only mode of ZK server so if a DC failed and remaining servers fail to
form a quorum, your application can still read data out of ZK, but no write
would be done after the point.

In general cross DC deployment design depends on your use case and trade
offs you'd like to make. Similar topic was well discussed before [1], and
there is a recent paper [2] which also provides good reference on this
topic.

[1]
http://zookeeper-user.578899.n2.nabble.com/zookeeper-deployment-strategy-for-multi-data-centers-td7582358.html#a7582364
[2]
https://www.usenix.org/system/files/conference/atc16/atc16_paper-lev-ari.pdf

On Thu, Dec 8, 2016 at 10:16 AM, Alvaro Gareppe <agareppe@gmail.com> wrote:

> I have Zookeeper running in a PRD environment with 3 instances running. 2
> in 1 data center and 1 in other. But as zookeeper ensamble runs with a
> majority if a loose the data center that runs 2 nodes of zookeeper, I loose
> the cluster.
>
> Is there any way to configure zookeeper (even adding more nodes is an
> option) to keep running if some of the data center is offline (any one of
> them). The only restiction, of course, is the number of datacenters
>
> --
> Ing. Alvaro Gareppe
> agareppe@gmail.com
>



-- 
Cheers
Michael.

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