We have lately started using syslog to hold the mongodb logs. However, it is a little overwhelming within the amount of informational logs we receive.

Also, since enabling the --syslog flag the system has decreased in performance

The below links describe, 0 is the default verbosity level and includes informational logs. How 1 - 5 only increases the verbosity level, is there a way to only log warning, error or fatal messages?

http://docs.mongodb.org/manual/reference/method/db.setLogLevel/

http://docs.mongodb.org/manual/reference/log-messages/