I'm not inserting anything and running out of space on my 32-bit machine.

I'm testing out replica pair failover with a driver. Every couple seconds I kill the master db server (call it A), wait for the other db (B) to become master, and restart A. Then I kill B, wait a couple seconds, restart B, repeat. After ~ 20 minutes of this, when I try to restart one of them, I get:

mmap() failed for /home/k/dbs/data2/local.7 len:536870912 errno:12
mmap failed with out of memory, if you're using 32-bits, then you probably need to upgrade to 64
Thu Dec 17 12:33:06 User Exception can't map file memory - mongo requires 64 bit build for larger datasets
Thu Dec 17 12:33:06 exception in initAndListen std::exception: can't map file memory - mongo requires 64 bit build for larger datasets, terminating

data2 contains:
local.0 local.2 local.4 local.6 local.ns
local.1 local.3 local.5 local.7 mongod.lock

I'm not doing anything other than querying and restarting the server, so it seems weird it's taking up 2GB so quickly, even if it is logging stuff.