The Dufferin papers comprise c.96,000 documents and c.850 volumes, 1605, 1630 and 1651-1940, relating to the estates and political achievements of the Blackwood family of Clandeboye, near Bangor, Co. Down, Lords Dufferin and Marquesses of Dufferin and Ava. These archives are kept at the Public Record Office of Northern Ireland (PRONI).
Reseach into the family archive and its connections with other important archives is co-ordinated at Clandeboye by Lola Armstrong. However there are numerous links available on the internet into the history of Clandeboye and its family, the Blackwoods, whose titled name is Dufferin and Ava.
If you are interested in family research the best starting point is probably the PRONI website