I'm currently evaluating MongoDB for storing large datasets. After inserting a significant amount of data (perhaps 4GB based on the mongod process size?) inserts start failing with messages like the following:

Tue Feb 16 10:41:18 insert test_database.archive2 exception userassert:can't map file memory 0ms
mmap() failed for /home/msmits/mongo-data/test_database.7 len:2146435072 errno:12
mmap failed with out of memory, if you're using 32-bits, then you probably need to upgrade to 64
Tue Feb 16 10:41:18 test_database.archive2 Caught Assertion insert, continuing

I was under the impression that this should only happen on 32-bit systems. At the point of failure there is still several GB of physical memory available.

I am able to reproduce this problem with all the 64-bit builds on the downloads page (1.2.2, 1.2 latest, 1.3.2 and 1.3 latest).

See the attachment for a sample Python client script that reproduces the problem. On my machine it takes approx 15 mins for the failure to occur.