Optimal data placement on networks with a constant number of clients

We introduce optimal algorithms for the problems of data placement (DP) and page placement (PP) in networks with a constant number of clients each of which has limited storage availability and issues requests for data objects. The objective for both problems is to efficiently utilize each client's storage (deciding where to place replicas of objects) so that the total incurred access and installation cost over all clients are minimized. In the PP problem an extra constraint on the maximum number of clients served by a single client must be satisfied. Our algorithms solve both problems optimally when all objects have uniform lengths. When object lengths are non-uniform we also find the optimal solution, albeit a small, asymptotically tight violation of each client's storage size by εlmax where lmax is the maximum length of the objects and ε some arbitrarily small positive constant. We make no assumption on the underlying topology of the network (metric, ultrametric, etc.), thus obtaining the first non-trivial results for non-metric data placement problems. © 2013 Elsevier B.V