公式サイトでは下記のような見解が述べられています。 32-bit limitations http://blog.mongodb.org/post/137788967/32-bit-limitations 32-bit MongoDB processes are limited to about 2 gb of data. This has come as a surprise to a lot of people who are used to not having to worry about that. The reason for this is that the MongoDB storage engine uses memory-mapped files for performance. By not supporting more than 2gb on 32-bit, we