A common perception of archives and libraries is that these are fundamentally different and they do not cooperate well or willingly. There are exceptions of course. At National Library New Zealand (Te Puna Mātauranga o Aotearoa) and Archives New Zealand (Te Rua Mahara o te Kāwanatanga) we found ourselves in a situation where very close cooperation in digital preservation field was the only way to tackle and make progress with digital preservation. We have been using and sharing one instance of the Rosetta preservation system since 2012. This presentation describes this digital preservation collaboration - how it came into place, some of the challenges and benefits and where we stand now. It also describes the wider context in which this collaboration has taken place and other areas where we’ve explored collaboration.