An optimization-based approach is presented that determines how plant feedstocks should be allocated to storage when there are fewer storage vessels than feedstocks. It is assumed here that material from the storage vessels will be subsequently blended for processing in downstream processes. The objective of the feedstock allocation strategy is chosen to ensure maximum flexibility for downstream process operation. Given the stated objective for feedstock allocation and the physical constraints, the feedstock storage allocation problem is posed in optimization form. The solution of the resulting singular-value optimization problem is discussed in terms of semidefinite programming techniques. The ideas presented are illustrated using a crude-oil storage case study. Finally, a number of observations regarding useful extensions to the proposed methods are presented.