Issue title: how does elasticsearch store data
 Issue body: we are trying to use elasticsearch, logstash and kibana to manage our logs. We have several questions about the storage of data. Could you please to help us to figure it out, please? when elasticsearch gets all logs, where does it store them? Because we have about 200G logs every day, so we want to know whether elasticsearch could remove old logs automatically. If it does, how can we set that up and how long will it keep data?
thank you

 Comments: 
 Comment 0: Elasticsearch will store data as long as it has disk space on its nodes.  Its stores this on the local disk, for details on where take a look at http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/setup-dir-layout.html#setup-dir-layout

You can manage the retention with Elasticsearch Curator (https://github.com/elasticsearch/curator).

You may also want to ask these sorts of questions on the Elasticsearch mailing list at https://groups.google.com/forum/#!forum/elasticsearch.

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