## 5 Simulation
### Experiment for SC Policy Performance Verification  
This section presents the performance evaluation of the proposed SC policy for an effective algorithm for VM consolidation. The HS sets NS-HS as the parameters that show the best results in the previous experiment. A comparative analysis is conducted with the FFD, which was the most commonly applied heuristic algorithm in previous studies. The THR, MAD, and IQR policies are applied for VM consolidation as PM overload is detected during VM migration. The DMA, MMC, and SC policies proposed in this study are applied for to select the VMs to migrate during PM overload detection. The FFD and NS-HS are applied to determine the destination PM for the selected VMs for migration. Based on the above three policies of the source PM selection and three policies of VM selection, a total of nine combinations were compared and tested. The experimental results are shown in Figures 9a-c and 10a-c shows the graph representing the performance measure results for each algorithm combination. Figure 9a-c shows the results of comparing power consumption, VM migration cost, and VM migration count, which are the performance measures related to the objective function, for each combination. By applying VM consolidation, the power consumption was reduced in all combinations, and the power savings of the NS-HS were better than those of the FFD. The SC policy combination proposed in this study showed less improvement in terms of power savings compared to other VM selection combinations. However, it showed improvement in terms of VM migration cost and number of VM migrations. The THR-SC combination with the best migration cost showed about 77.15% improvement compared to the worst MAD-DMA, and number of migrations, which is the best THR-SC combination, showed about 53.15% improvement over the worst THR-DMA combination. The results of the NS-HS versus FFD were better in terms of performance measures associated with the overall objective function, and the combination with the SC policy was less effective in terms of power usage than the other combinations, but improved in terms of VM migration, which is applied as the penalty in VM consolidation. Figure 10a-c shows the results of the SLATAH, PDM, and SLAV values, which are the performance measures related to the quality of the DC operating environment. Similarly, in the performance measure, the NS-HS produced better results than the FFD. When comparing the SC policy combinations and other combinations based on the NS-HS, SLATAH showed about 26.22% improvement over the DMA combination and about 30.03% improvement over the MMC combination. PDM also showed about 31.25% improvement over the DMA combination and about 33.33% improvement over the MMC combination; SLAV, which is the product of SLATAH and PDM, showed an improvement of about 33.33-62.25%. Through these results, it is confirmed from the experimental results that the VM consolidation model considering the SC combination contributes toward stable DC operation. The proposed HS showed excellent results in every aspect of the objective value, such as power savings and migration cost, and also displayed good results for SLATAH and PDM, which are the aspects of SLAV, an indicator of DC operation quality. In particular, when the SC policy, which searches for a combination of VMs in which the workload of the PM is stably maintained, was applied, the power consumption was relatively high compared to other policies, but the effect of VM migration was relatively largely reduced. This showed excellent results in terms of the quality of the DC operation environment; it can thus be concluded that the proposed VM consolidation model meets the requirements of DCs that prioritize stability. Figure 9: **(a)**. Comparative experimental results of performance measures to the power consumption. **(b)**. Comparative experimental results of performance measures to the migration cost. **(c)**. Comparative experimental results of performance measures to the number of migrations. Figure 10: **(a)**.