In this paper we focus on the problem of data aggregation using two aggregators in a data center network, where the source racks are allowed to split their data and send to the aggregators using multiple paths. We show that the problem of finding a topology that minimizes aggregation time is NP-hard fork = 2, 3, 4, where k is the maximum degree of each ToR switch (number of uplinks in a top-of-rack switch) in the data center. We also show that the problem becomes solvable in polynomial time fork = 5 and 6 and conjecture the same for k > 6. Experimental results show that, for k = 6, our topology optimization algorithm reduces the aggregation time by as much as 83.32 percent and reduces total network traffic by as much as 99.5 percent relative to the torus heuristic, proposed in [1], which readily proves the significant improvement in performance achieved by the proposed algorithm.