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Date: Tue, 25 May 2010 07:38:20 +0530
Message-ID: <AANLkTil1XC1QF5XeGhGK_ZsQzXHaG5tNcRrNt9S2okSW@mail.gmail.com>
Subject: Re: Active-Active Performance
From: Hemanth Yamijala <yhemanth@gmail.com>
To: general@hadoop.apache.org
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Anthony,

I=92m new to Hadoop and I=92ve been given the task to see how we might util=
ise
> Hadoop and HBase to implement an Active-Active site layer for sharing
> information across a distributed application.
>
>
>
> I=92ve been able to:
>
> =B7         Install and get Hadoop running on a single node and am in the
> process of configure a 2 node setup.
>
> =B7         Install HBase on a single node and create a table and mapping=
 as
> well as insert data into the system
>
>
>
> Once I=92ve got the mutli-node configured I hope to run some tests as wel=
l.
>
>
>
> I=92ve noticed that trying to start Hadoop in distributed mode, the slave
> will ssh to the master to start it as well (bin/start-all.sh) provided th=
e
> same path is setup on the remote machine.
>
>
>
> Questions:
>
> Can I configure the system IF the Hadoop installation is not in the same
> location per machine?
>

I would think configuring and managing such a system would get very complex
- for e.g. if you'll want to add nodes to expand in future. You would also
not be able to take advantage of the very helpful scripts that come with
Hadoop. Is there a reason why you want to do this ?

> If the master node goes down (say due to electrical fault or system fault=
)
> how do the slave nodes react? Will they continue to run? Will the nodes b=
e
> back in sync once the master starts again?
>

Hadoop slaves will continue. They will enter a retry loop trying to connect
to the master until it comes up. In doing so, they could fill up log files
very fast though. If the master starts with the same configuration, (same
host, ports), they should be able to connect and resume.

> Would I require a particular configuration to ensure that both our sites
> can operate within the cluster as well as in a detached fashion (due to
> maintenance or network issues)?
>
>
>
I did not quite follow this. Can you explain a little more about how you
want to setup your system ?

Thanks
Hemanth

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