If as an archive you have decided that the provision of your mass storage is best left as an activity that you contract out, the choice is then how far to take that out sourcing. Many archives exist as departments within wider institutions and the outsourcing of storage to the IT part of the parent organisation is a valid and viable option in many circumstances. Such a move still requires careful preparation and contractual documentation however, as many of the requirements of an archive may well differ from the standard approaches to data storage within an IT department.
Alternatively, if your organisation does not contain the required capabilities at any level, or for other reasons it is impractical to outsource in the way described above, you will want to look outside your organisation for a solution provider. Institutional outsourcing as we have called this, also gives you further options which you can explore.