How to stress test a mongodb?
After quite some research I came to the point to use jmeter to do massive REST calls. That way I can create a controlled load on the database. The profiling I do with node-inspector and native mongodb profiling.
For those who like to do a more "direct" test to the DB John Page's POCDriver (simulated client): https://github.com/johnlpage/POCDriver might be interesting.
Profile visualisation (from log files) can be done with: https://github.com/rueckstiess/mtools
Hope that helps :-)