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From Alex Loddengaard <a...@cloudera.com>
Subject Re: Does the HDFS client read the data from NameNode, or from DataNode directly?
Date Fri, 10 Apr 2009 17:43:18 GMT
Data is streamed directly from the data nodes themselves.  The name node is
only queried for block locations and other meta data.


On Fri, Apr 10, 2009 at 8:33 AM, Stas Oskin <stas.oskin@gmail.com> wrote:

> Hi.
> I wanted to verify a point about HDFS client operations:
> When asking for file, is the all communication done through the NameNode?
> Or
> after being pointed to correct DataNode, does the HDFS works directly
> against it?
> Also, NameNode provides a URL named "streamFile" which allows any HTTP
> client to get the stored files. Any idea how it's operations compare in
> terms of speed to client HDFS access?
> Regards.

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