On the Hanrahan side, most of my ancestors were Irish from Galway in the townland of Garryad and Garryduff in the parish of Killimor. I can find records back to about 1800, but not before.
On my Scottish/Irish MacDonald side, 25% of my family is from Nova Scotia. I've found DNA matches and records for their time in Nova Scotia. But tracing them back to Ireland has been difficult, especially for my 5th great-grandfather, Cornelius Dwyer (born about 1742 in Tipperary, Ireland.)
Also on the MacDonald side, I have had difficult tracing my 2nd great grandparents, Patrick and Bridget Griffin (born around 1825) before their time on Long Island in New York. There are lots of records and several DNA matches for their time in New York, but not before. I'm pretty sure they came from Ireland on one of the "famine ships" in the 1840s, but I can't sort out which of several Patrick Griffins he was, or where in Ireland.
I find the intersection of personal and world history to be really interesting and would like to learn more about the pre-1700 period, not to mention pre-1800!