Hold entire Neo4j graph database in RAM?

Question

I'm researching graph databases for a work project. Since our data is highly connected, it appears that a graph database would be a good option for us.

One of the first graph DB options I've run into is neo4j, and for the most part, I like it. However, I have one question about neo4j to which I cannot find the answer: Can I get neo4j to store the entire graph in-memory? If so, how does one configure this?

The application I'm designing needs to be lightning-fast. I can't afford to wait for the db to go to disk to retrieve the data I'm searching for. I need the entire DB to be held in-memory to reduce the query time.

Is there a way to hold the entire neo4j DB in-memory?

Thanks!

Answer 1

Further to Bruno Peres' answer, if you want to run a regular server instance, Neo4j will load the entire graph into memory when resources are sufficient. This does indeed improve performance.

The Manual has a chapter on configuring memory.

The page cache portion holds graph data and indexes - this is configured via the dbms.memory.pagecache.size property in neo4j.conf. If it is large enough, the whole graph will be stored in memory.

The heap space portion is for query execution, state management, etc. This is set via the dbms.memory.heap.initial_size and dbms.memory.heap.max_size properties. Generally these two properties should be set to the same value, so that the whole heap is allocated on startup.

If the sole purpose of the server is to run Neo4j, you can allocate most of the memory to the heap and page cache, leaving enough left over for operating system tasks.

Holding Very Large Graphs In Memory

At Graph Connect in San Francisco, 2016, Neo4j's CTO, Jim Webber, in his typical entertaining fashion, gave details on servers that have a very large amount of high performance memory - capable of holding an entire large graph in memory. He seemed suitably impressed by them. I forget the name of the machines, but if you're interested, the video archive should have details.