title: best graph database for saving millon of node
body: <p>I want to ask a question about graph database.</p>
  
  <p>First im using networkx in python and creating graph in memory, but when i reach more nodes - my RAM was not enough.</p>
  
  <p>So, for next time i try to neo4j. Its nice, write graph on disk, but its slow(how i think. With index and other things, more slow than networkx). Now i create 500k nodes and 2000000 relationships, try to find path between two nodes, and neo4j just stuck on my server. </p>
  
  <p>I hear about orientdb, but not try yet now.</p>
  
  <p>So, i need advice, what the best graph database, who can write graph on disk?</p>
  
  <p>Big thanks to you.</p>
  
  <p>PS want only open-source graph database</p>