Titan: Does Elastic Search store mixed indexes externally?
in titan you can choose to create 2 different indexes:
Simple titan index
Index using external system such as Solr or ElasticSearch
In the second case Elastic Search will create external index files, differents from the Titan ones.
You can take a look to my gist and create a in-memory graph with Elastic Search, create an Elastic Search index on a property, for example, and check it out.
The answer is yes, Elastic Search will create external files in your server for indexes.
If you dislike this, you could use Titan's composite index. Composite indexes use the indexing mechanism of the backend storage you're using (e.g., berkeleyj, cassandra, etc). This means that all indexing will be inside the backend.
For more information, have a look here.