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Date: Thu, 14 Jan 2010 12:40:48 -0800
Message-ID: <b54edc3a1001141240k752f415by740034d95e5fcd8a@mail.gmail.com>
Subject: Re: Question regarding Membership Election
From: Henry Robinson <henry@cloudera.com>
To: zookeeper-user@hadoop.apache.org
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Hi -

If you put all your voting nodes in one datacenter, that datacenter becomes
a 'single point of failure' for the cluster. If it gets cut off from any
other datacenters, the cluster will not be available to those datacenters.

If you want to withstand the failure of datacenters, then you need voting
members inside every datacenter. Observers can't suddenly become voting
members.

You can't even put 'dormant' voting members (that never bother to vote) in
your other datacenters because you would need a quorum of them to continue
after the original datacenter failed. And if this was true, the original
datacenter would not, by construction, contain a quorum of voting nodes. So
you'd still have to vote outside the cluster.

Henry

2010/1/14 Vijay <vijay2win@gmail.com>

> Hi,
>
> I read about observers in other datacenter,
>
> My question is i dont want voting across the datacenters (So i will use
> observers), at the same time when a DC goes down i dont want to loose the
> cluster, whats the solution for it?
>
> I have to have 3 nodes in primary DC to accept 1 node failure. Thats
> fine...
> but what about the other DC? how many nodes and how will i make it work?
>
> Regards,
> </VJ>
>

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