1. A method for placing N applications on M virtualized servers, said servers having power management capability, said method comprising the steps of: dividing a time horizon into a plurality of time windows; for each given one of said windows, computing a placement of said N applications, taking into account power cost, migration cost, and performance benefit, wherein said migration cost refers to cost to migrate from a first virtualized server to a second virtualized server for said given one of said windows, and wherein said computing comprises minimizing overall cost in accordance with: minimize ⁢ ⁢ ∑ j = 1 M ⁢ P ⁡ ( A I ) + Mig ⁡ ( A o , A I ) wherein: A o comprises an old allocation of said applications to said servers; P(A) comprises a power cost function modeling said power cost; Mig comprises a migration cost function, modeling said migration cost, for any allocation A; and A I comprises an allocation defined by variables x i,j , where x i,j denotes resource allocated to application V i on server S j ; and placing said N applications onto said M virtualized servers, for each of said plurality of time windows, in accordance with said placement computed in said computing step for each of said windows.