Neunhoef added a comment.

> OK.  Maybe its just a function of not using a super nice machine for testing. 
>  We really do want the system to scale down to work with less ram and cheap, 
> big spinning disks so folks can run it on their laptop.  That'll encourage 
> experimentation.


Well, ArangoDB is designed to be a "mostly-in-memory" database, which means 
that it really likes to keep all its data including indexes in main memory. The 
actual data is persisted using memory mapped files, but all access patterns 
essentially assume that all data is available in RAM. By the way, most of your 
candidate graph databases (Neo4j, OrientDB, Wikidata Query service) use this 
approach. Only Titan/Cassandra would run well with less RAM than data. 
Therefore, if you want this, you have to use a corresponding engine, and this 
will probably mean Titan.
However, you also said that you want to index by essentially all attributes. If 
this is true, then you will face a dilemma with any database solution: Either 
at least some queries are untolerably slow, because the actual data or the 
particular index you access needs to be swapped in, or everything fits into 
RAM, in which case it will be cached there. This is because you have 
essentially unpredictable random accesses to your data.
So I would expect that even with an essentially disk-based database engine you 
will run into problems and due to the virtualisation features of modern OSes 
you will get the same performance behaviour with a mostly-in-memory database 
like ArangoDB for your scenario.


TASK DETAIL
  https://phabricator.wikimedia.org/T88549

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To: Smalyshev, Neunhoef
Cc: Neunhoef, Fceller, JanZerebecki, Aklapper, Manybubbles, jkroll, Smalyshev, 
Wikidata-bugs, aude, GWicke, daniel



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