The Sedona Conference® Working Group 1 recently published a Commentary on the issues of preserving, managing, and identifying not reasonably accessible electronically stored information or “NRA ESI". The result is a five-step framework for analysis and six Guidelines for making reasonable, good-faith assessments where no “bright line” rules exist. Ira P. Rothken is a co-editor of the above Sedona Conference Publication entitled Commentary on Preservation, Management and Identification of Sources of Information that are Not Reasonably Accessible.which can be downloaded here and here is a web seminar  on the topic. Here is an excerpt of Ira P. Rothken discussing technical factors to consider in determing whether e-discovery related data is "not reasonably accessible."