2015-06-04T10:20:40.494-0400 [initandlisten] ** WARNING: Readahead for DBPATH is set to READAHEAD_VALUE
2015-06-04T10:20:40.494-0400 [initandlisten] **          We suggest setting it to 256KB (512 sectors) or less
2015-06-04T10:20:40.494-0400 [initandlisten] **          http://dochub.mongodb.org/core/readahead

http://dochub.mongodb.org/core/readahead links to http://docs.mongodb.org/manual/administration/production-notes/#readahead, where we recommend:

Ensure that readahead settings for the block devices that store the database files are appropriate. For random access use patterns, set low readahead values. A readahead of 32 (16kb) often works well.
For a standard block device, you can run sudo blockdev --report to get the readahead settings and sudo blockdev --setra <value> <device> to change the readahead settings. Refer to your specific operating system manual for more information.

These 2 suggestions are inconsistent. We should just refer to the docs and keep our recommendation in one place.