“…Incontrasttotheabovescenario,sometimestheworkloadonclouddatacentermaybeless.But thenumberofactiveserversisveryhighkeepinginmindthecertainriseindemandduringpick hours.Topreventthewastageofenergycloudcontrollertriestoconsolidatetheloadonlessnumberof activeserversbymigratingtheVMsfromunder-utilizedhosts;sothattheidleserverscanbeswitched offtosaveenergy.Ithelpstoachievegreencomputing (Xu,Liu,Jin,&Vasilakos,2014).Duetothe recentpopularityofdeployingmulticorearchitecturesystemsindatacenters,VMconsolidationisnow widelyusedtoimprovetheresourceutilizationofsuchphysicalservers (Lv,Dong,Duan,&Tian, 2012)andreducetheenergyconsumptionofdatacenters (Zhu,Zhu,&Agrawal,2010).Asmore VMsarecolocatedonthesamephysicalserver,VMconsolidation,however,increasestheseverity (Xu,Liu,Jin,&Vasilakos,2014).So,likethepreviousscenarioifrestrictionisnot imposedonVMconsolidationthenalsoaftersometimesomeoftheserverswillbecomeoverloaded andtheymayagaininitiateVMmigration.InthiswayrepeatedmigrationofthesameVMmayoccur. ThisscenarioisdepictedinFigure2.…”