When doing and import with mongoimport using dbpath, ex:
mongoimport -d Testing -c Joy --fields uid,name,activity --type csv --file /mnt/Testing.csv --dbpath /mnt/mdb/

The .ns file created will be 16M even though the config file and current setting is 2G for the ns file (our local config).

The solution is to either add a -c option to mongoimport so it can read the config file settings or add the --nssize setting.

Without this, after every import the db has to be repaired.