Disable Journaling in MongoDB + WiredTiger
When running a journal disabled cluster, we observed frequent disk checkouts - once about every 3 seconds. This was confusing, as the docs specifically mention that checkpoints are created every 60 seconds.

After digging around, we found the following comment on mongo's Jira:


  ... it is expected that the primary node executes a checkpoint whenever there are multiple write threads as this checkpoint ensures that writes to the replica set are durable


This means that when journaling is disabled, and there are multiple threads writing to the DB, checkpoints become frequent and slow down the entire instance.

This, of course, was a sufficient reason for us to turn on journaling again.