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From Tatsuya Kawano <tatsuy...@snowcocoa.info>
Subject Re: recovering from zookeeper failures
Date Wed, 11 Nov 2009 01:28:42 GMT
hi ishwar,

> I read that zookeeper needs a simple majority to recover from failures.
> So is 2 same as 1 as far as recovery goes?

Yes. When they lost contact with other (e.g. by a network disruption),
they both stop serving because they can't say "I'm in the majority."


> Does it help in load balancing.

I don't find a clear answer for this in ZK documents, but I found this
JIRA says "Clients randomly connect to a server, which typically
balances the number of sessions", so the answer should be yes.

https://issues.apache.org/jira/browse/ZOOKEEPER-571


> If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
> zoo keeper server (replace) can i recover the tables?

When ZK ensemble becomes unavailable, HBase master and region servers
think they are disconnected from the HBase cluster, so they shutdown
gracefully. You shouldn't loose any data by this, but you have to
start the HBase cluster again once ZK ensemble becomes available.


Thanks,

-- 
Tatsuya Kawano (Mr.)
Tokyo, Japan



On Wed, Nov 11, 2009 at 9:34 AM, ishwar ramani <rvmishwar@gmail.com> wrote:
> Hi,
>
> I am setting up a simple hbase system. I currently have a 2 node
> clsuter server for
> the zookeeper servers ...
>
> I read that zookeeper needs a simple majority to recover from failures.
> So is 2 same as 1 as far as recovery goes? Does it help in load balancing.
>
> If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
> zoo keeper server (replace) can i recover the tables?
>
> thanks
> ishwar

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