Spot on. I came here to say just this. Dev branch or not, there is no way he could have missed this. I don't know how you can better advertise a limitation than

Spot on. I came here to say just this. Dev branch or not, there is no way he could have missed this. I don't know how you can better advertise a limitation than this. Maybe he didn't realize he was on a 32-bit box. Maybe he didn't pay attention to how much data he would be using. If you want to use Mongo for something serious, make sure you're on a 64-bit box. Memory-mapped file I/O is an important part of what makes Mongo so fast and attractive, but it has obvious limitations on a 32-bit box.