I have not heard of any 2 year active + 6 year IRR contracts, but then I am the mom of a Sailor, so I do not have access to all info on that. I have heard of 4+4 (standard) and 6+2 (for SEALS and special ops and a few specialized ratings). http://www.navy.com/navy/joining/qualifications.html indicates "Enlisted positions typically require an initial service commitment of two to four years (positions involving longer-term training may involve longer service obligations)." That would suggest that 2+6 is possible. I like this statement from that site, "The best way to confirm the specific service commitment that will apply to you is to contact a recruiter."
Read my reply and the replies after it at http://www.navyformoms.com/forum/topics/first-visit-to-meps-in-janu... (clickable link). That will give you info on parents going to MEPS.