## 3 Scheme of the IVM-ReU  
The idle virtual machine-resource utilization (IVM-ReU) scheme that provides cloud computing services by selecting idle virtual machines present in OpenStack is shown in Figure 1. Figure 1-1 shows that large-scale applications (i.e., jobs) submitted by requester (i.e., users) through OpenStack's Dashboard (i.e., IVM-ReU Website), are transferred to the IVM-ReU Manager. Figure 1-2 shows the process of searching and selecting virtual machines that exist idle to handle requested tasks. Figure 1-3 shows that selected idle virtual machines are managed in a single pool, collecting static information such as the number of CPUs, total memory size, and dynamic information such as memory usage, the state of idle virtual machines. The information collected is transferred in the form of metadata to the IVM-ReU Manager as shown in Figure 1-4. The metadata of idle virtual machines allows IVM-ReU Manager to manage the state of idle virtual machines, which is based on which it designates some idle virtual machines as workers to handle tasks. Figure 1-5 shows the process of dividing and transferring a large-scale job into uniform-size tasks. These partitioned tasks are stored in the IVM-ReU Task  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Paper Title**} & \multirow{2}{*}{**Framework**} & **Idle Virtual** & **Virtual** & **Various** & **Computing** \\  & & **Machine** & **Machine** & **Virtual** & **Service** \\  & & **Considered?** & **Recycle** & **Machine Specs** & **Provided** \\ \hline CloudGC: Recycling Idle Virtual Machines in the Cloud & OpenStack & O & O & O & X \\ \hline Efficient Dynamic Resource Allocation Using Nephele in a Cloud Environment & Nephele & O & X & O & X \\ \hline OpenStack Next a framework for dynamic and energy-efficient consolidation of virtual machines in OpenStack Clouds & OpenStack & O & O & O & X \\ \hline Optimized Virtual Resource Development using CloudSim & CloudSim & O & O & X & X \\ \hline Advanced Memory Reusing Mechanism for Virtual Machines in Cloud Computing & CloudSim & O & O & X & X \\ \hline Our Proposed Scheme & OpenStack & O & O & O & O \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of the idle virtual machine–resource utilization (IVM–ReU) with previous studies.  
Saver before they are sent to workers. Figure 1-5 assigns split tasks to each worker in IVM-ReU Task Saver, and shows how each worker processes the tasks. Tasks that have been processed are sent to the IVM-ReU Task Saver as shown in Figure 1-5. Figure 1-5 shows the process of transferring the processed tasks from the IVM-ReU Task Saver to the IVM-ReU Manager. The transmitted tasks are merged into a single job as shown in Figure 1-5 and presented to the requester (i.e., user) via the IVM-ReU Web site (i.e., OpenStack Dashboard).  
IVM-ReU largely consists of three parts: Idle Virtual Machine Selection, which searches for and selects virtual machines in an idle state among virtual machines generated in OpenStack; Idle Virtual Machine Pool, which collects dynamic and static information to manage selected idle virtual machines; and Computing Service with Idle Virtual Machine, which provides computing services by distributing the partitioned large-scale jobs into each of the idle-state virtual machines.