http://docs.mongodb.org/manual/reference/configuration-options/

A number of mmapv1-specific configuration file options have been renamed to include "mmapv1" in the dotted name. The old names are still supported and will trigger a startup warning when used.

Here's a list of the updated options:

• storage.mmapv1.directoryPerDB
• storage.mmapv1.journal.commitIntervalMs
• storage.mmapv1.journal.debugFlags
• storage.mmapv1.nsSize
• storage.mmapv1.preallocDataFiles
• storage.mmapv1.quota.enforced
• storage.mmapv1.quota.maxFilesPerDB
• storage.mmapv1.smallFiles
• storage.mmapv1.syncPeriodSecs

Additionally, it is a warning to provide configuration options for a storage engine that is currently active. For example, if the heap1 storage engine is selected using the `--storageEngine=heap1` option, mongod will log an error at startup if it detects any mmapv1 options on the command line or in the configuration file.