As discussed on this List in the past, you can't get client file sizes from server queries, so there is no way therein to sum the savings of changing retention policies. You could approach it on the basis of client queries on Inactive files. Another approach is proportion: if you have a good idea of the population of Inactive files relative to total possible population per your retention policies, then reducing the policy number by a certain percent would result in a proportional percent drop in your current server storage pool numbers.
Richard Sims, BU
