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From Doug Cutting <cutt...@apache.org>
Subject Re: Namenode Exceptions with S3
Date Thu, 17 Jul 2008 17:16:40 GMT
Tom White wrote:
> You can allow S3 as the default FS, it's just that then you can't run
> HDFS at all in this case. You would only do this if you don't want to
> use HDFS at all, for example, if you were running a MapReduce job
> which read from S3 and wrote to S3.

Can't one work around this by using a different configuration on the 
client than on the namenodes and datanodes?  The client should be able 
to set fs.default.name to an s3: uri, while the namenode and datanode 
must have it set to an hdfs: uri, no?

Would it be useful to add command-line options to namenode and datanode 
that override the configuration, so that one could start non-default 
HDFS daemons?

> It might be less confusing if the HDFS daemons didn't use
> fs.default.name to define the namenode host and port. Just like
> mapred.job.tracker defines the host and port for the jobtracker,
> dfs.namenode.address (or similar) could define the namenode. Would
> this be a good change to make?

Probably.  For back-compatibility we could leave it empty by default, 
deferring to fs.default.name, only if folks specify a non-empty 
dfs.namenode.address would it be used.

Doug

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