What are the best ways to store Graphs in persistent storage

Question

I am wondering what the best ways to store graphs in persistent storage are, for later analysis, search, clustering, etc.

I see neo4j being an option, I am curious if there are also other graph databases available. Does anyone have any insights into how larger social networks store their graph based data (or other sites that require the storage of graph like models, e.g. RDF).

What about options like Cassandra, or MySQL?

Answer 1

Graph Databases:

1. HyperGraphDB: a general purpose, extensible, portable, distributed, embeddable, open-source data storage mechanism.
2. InfoGrid: an Internet Graph Database with a many additional software components that make the development of REST-ful web applications on a graph foundation easy.
3. vertexdb: a high performance graph database server that supports automatic garbage collection.

Source: http://nosql.mypopescu.com/post/498705278/quick-review-of-existing-graph-databases

Graph Libraries:

1. WebGraph is a framework to study the web graph. From their page - "It provides simple ways to manage very large graphs, exploiting modern compression techniques."
2. Dex is a high performance library to manage very large graphs or networks.
3. This blog post - On Building a Stupidly Fast Graph Database - provides some guidelines on building a graph database - the technique they use is "memory-mapped I/O, disk-based linear-hashing".

Answer 2

Disclaimer: I am speaking form the graph analysis standpoint.

There are several file formats for storing graph data: GraphML, GXL and several others. But storage usually is not a problem. Working with the graphs without fully loading them into RAM is the tricky part.

The RDF model is too generic to do serious graph analysis stuff. If you don't mind your analysis being slow and programming the algorithms yourself, go with the existing graph databases - see wikipedia on this.

For real analysis, load all data into RAM using existing graph analysis libraries, like SNAP or see This question.