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To: "<common-user@hadoop.apache.org>" <common-user@hadoop.apache.org>,
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Subject: Re: Changing hostnames of tasktracker/datanode nodes - any problems?
Thread-Topic: Changing hostnames of tasktracker/datanode nodes - any
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On Aug 10, 2010, at 10:54 AM, Bill Graham wrote:
> Is is correct to say that that would work fine? We have a replication fac=
tor
> of 2, so we'd be copying twice as much data as we'd need to so I'm sure
> there's a more efficient approach.

It should work fine.  But yes, highly inefficient.

> What about adding the new nodes in the new colo to the existing cluster,
> rebalancing and then decommissioning the old cluster nodes before finally
> migrating the NN/SNN? I know Hadoop isn't intended to run cross-colo, but
> would this be a more efficient approach than the one above?

If you can keep both grids up at the same time, use distcp to do the copy. =
 This will make sure the blocks get copied once, will keep permissions with=
 -p, keep the replication factor, redistribute data (free balancing!), etc,=
 etc, etc.