Mongodb Journalling

A quick one if you are wondering about MongoDB and Journalling (especially on Debian/Ubuntu from the MongoDB repo) .

By default mongodb will generate 3gig of journal files in /var/lib/mongodb/journal this is far from ideal if you are running on a Rackspace CloudServer or smaller VPS.

There are two easy solutions:

• If you are running as part of a ReplicaSet then you can choose to go without journalling altogether with the

  nojournal=true

  option in mongodb.conf.
• Alternatively you can request that MongoDB uses smaller preallocated files for journalling use the

  smallfiles=true

  option in mongodb.conf.

To also reduce some usage in your datafiles there is the also the

noprealloc = true

option, however I don’t see this as particularly useful considering the preallocation starts pretty small and only grows as your data does.