问题
I saw that by default, a MongoDB has 24,000 collections available with a 16MB .ns file. If I increase that to 2GB (the max), can I then get 3,000,000 collections in a DB? Will there be any substantial performance decrease?
回答1:
According to documentation large number of collections will not affect performance (almost not).
having a large number of collections has no significant performance penalty, and results in very good performance
If you need more collection you can increase .ns file via --nssize parameter up to 2GB.
Documentation
回答2:
I think thats the same as another DB... higher, it becomes more slower..
来源：https://stackoverflow.com/questions/7521664/how-many-collections-are-possible-in-a-mongodb-without-losing-performance