In a recent effort to strengthen active preservation strategies, Oregon State University Libraries committed to conducting a multi-part annual preservation assessment for our institutional repository, focusing on the sustainability of file formats. This spring we conducted the first assessment, gathered a lot of data, and uncovered a few holes in our knowledge. The presentation will discuss the specific actions involved in our preservation assessment and the benefits and limitations we identified in our approach. The presenter will demonstrate some surprising difficulties in counting assets; share how undertaking this assessment required a crash course in log querying; and try to answer the question of how much closer we are to our guarantee of future retrievability for the works held in the repository. The presentation will touch on CoreTrustSeal Trustworthy Repository certification, and how that certification process played a key part in articulating our digital preservation commitments. Finally, the presenter will discuss how we have learned from our experience so that we can do the whole thing perfectly next year.