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From Ritesh Tijoriwala <tijoriwala.rit...@gmail.com>
Subject Re: Question about Clustered Setup in two data centers
Date Wed, 02 Mar 2011 17:50:59 GMT
Hi Zsolt,
Do you have any operations that cross data centers besides when failover
happens and other data center takes over? Is only one data center "active"
at given time and other just for pure failover or both of them can be
active?

If only one of them is active, then why do you need ZooKeeper instances
across data center? For things that you replicate across data center, can
you afford them to be eventually consistent? Within a data center, you can
use ZooKeeper to reach agreement on a "value" and then once reached, you can
just blindly replicate this to other data center. Ofcourse, if the other
data center is also active, then you need to detect conflicts and resolve
them.

Thanks,
Ritesh

On Wed, Mar 2, 2011 at 8:19 AM, Mahadev Konar <mahadev@apache.org> wrote:

> Hi Zsolt,
>  Sorry to disappoint but there isnt any way of running zookeeper on 2
> machines and calling it reliable. You can run a set of 2 machines for
> a quorum of 3 but if one of the machine goes down then zookeeper goes
> down. Also, a data center of 2 has issues since which ever datacenter
> you place the max part of the quorum in, in case of death will caiuse
> the ZK cluster to fail.  I am assuming you are talking about ZK cross
> data center.
>
> thanks
> mahadev
>
> On Wed, Mar 2, 2011 at 6:57 AM, Zsolt Beothy-Elo <zbeothy-elo@talend.com>
> wrote:
> > Hi all,
> > in our product we currently implement to use ZooKeeper in conjunction
> with CXF to dynamically manage available services and endpoints.
> Unfortunately one of our customers is not very happy of having to run a
> minimum of three ZooKeeper server instances to ensure fail over. The
> customer has two data centers in different locations where data and
> applications are replicated and some big-ip appliance in front of the data
> centers. If one data center fails everything must still be operable. So he
> would prefer to only have two  instances one in each data center. I would be
> grateful for some advise how to best cope with these contradicting
> requirements.
> >
> > Cheers,
> > Zsolt Beothy-Elo
>

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