FWIW, here's the FAQ on performance with durability enabled:
How's performance?
Read performance should be the same. Write performance should be very good but there is some overhead over the non-durable version as the journal files must be written. If you find a case where there is a large difference in performance between running with and without --dur, please let us know so we can tune it. Additionally, some performancing tuning enhancements in this area are already queued for v1.8.1 and beyond.
FWIW, here's the FAQ on performance with durability enabled:
How's performance?
Read performance should be the same. Write performance should be very good but there is some overhead over the non-durable version as the journal files must be written. If you find a case where there is a large difference in performance between running with and without --dur, please let us know so we can tune it. Additionally, some performancing tuning enhancements in this area are already queued for v1.8.1 and beyond.