and thus rarely has the problem.

Thus, HA is much better than FFD in minimizing costs and improving resource utilizations in resource and task managements of hybrid clouds.

Figures \[rentcost\] and \[makespan\] show that the rent cost is decreased with increasing the deadline while the finish time increases with deadline. The reason is that tasks are allocated less resources, which leads to longer waiting time of tasks and thus longer time to finish these tasks, if their deadlines are postponed.

### Overhead & Scalability {#overhead}

In this section, we experimentally compare HA and FFD in overhead and scalability.

Figure \[time\] shows the time consumed by HA and FFD running on a Intel(R) Xeon(R) CPU E5410 @ 2.33GHz core. As shown in this figure, HA consumes less time than FFD when the deadline is early ($\alpha=1/2$), while it consumes more time than FFD when it is late ($\alpha=3/4$). The reasons are as follows. The time complexities of HA and FFD are $O(T\cdot(P+T+N_{RV}))$ and $O(T\cdot(P+N_{RV}))$, respectively. When the deadline is earlier, the number of rented VMs is larger. When $\alpha=1$ or 2, the number of rented VMs used by FFD is larger than 4000, as shown in Fig. \[VMnumber\], which is above 