“…All this considered, present studies on VM delay did not investigate the influence of VM migration on the total delay at the VMs, for the queueing models of VMs ignored the failure and migration of VMs [ 24 , 25 , 27 ], and the VM migration delay was measured separately from the total delay [ 12 , 13 , 14 , 42 , 44 , 45 , 46 , 47 , 53 ]. Meanwhile, due to the unique process of failure, migration, and recovery of VMs, present queueing models with unreliable servers [ 20 , 21 , 22 , 23 , 26 ] cannot be directly applied to analyze the VM delay.…”