Setup a 3 node replica set. Use separate servers or at least different data disk for each node. Using the following script, insert data into a collection: #!/bin/bash while true do TIME=`date` echo "db.test.insert( Unknown macro: { time } )" | mongo test done Use a tool like dd if=/dev/zero of=/tmp/eatspace bs=1024 count=1024 to fill the disk. Note that even after the disk is full, MongoDB will continue to successfully insert more data until the last 2 GB data file becomes full. What actually happens: Observe following errors from the insert: MongoDB shell version: 2.4.6 connecting to: test Can't take a write lock while out of disk space bye And in the log: Wed Aug 28 11:08:07.306 [FileAllocator] allocating new datafile /var/lib/mongo/test.2, filling with zeroes... Wed Aug 28 11:08:07.307 [FileAllocator] FileAllocator: posix_fallocate failed: errno:28 No space left on device falling back Wed Aug 28 11:08:07.307 [FileAllocator] error: failed to allocate new file: /var/lib/mongo/test.2 size: 268435456 failure creating new datafile; lseek failed for fd 22 with errno: errno:2 No such file or directory. will try again in 10 seconds What should happen When failing to allocate a new datafile, the primary should step down and allow another node to become primary. In addition, it should go into a state where it cannot become primary again (for example, if it has a high priority) until the problem has been fixed. Workarounds When noticing the failure, the DBA must call rs.stepDown() or shut down the failing mongod process. rs.stepDown() could also be called automatically from an application that receives disk full or other similar error message. In addition, it might make sense to set the node into hidden or priority=0 state until problem is fixed.