JP7675144B2 - Management device, management method, and program - Google Patents

Description

The present invention relates to a management device, a management method, and a program.

Currently, there is known technology that allows multiple virtual machines to run simultaneously on one server. For example, Patent Document 1 discloses a technology that determines the combination of virtual machines and virtual machine servers that maximizes the performance of each virtual machine.

JP 2005-115653 A

Some virtual machines running on a virtual machine server are used infrequently. For example, when using virtual machines in a testing environment, it is expected that the virtual machine being tested will be used frequently, but will be used less frequently once testing is complete. Therefore, it is considered inefficient to reserve the physical resources of the virtual machine server even for virtual machines that are used infrequently.

The present invention aims to provide a technology that enables efficient use of the physical resources of a virtual machine server based on the frequency of virtual machine usage.

A management device according to one aspect of the present invention includes an acquisition unit that acquires statistical information regarding the operation of a first virtual machine that is placed on a first virtual machine server that does not allow overcommitment, a calculation unit that calculates a score indicating the usage frequency of the first virtual machine from the statistical information, and a placement control unit that places the first virtual machine on the first virtual machine server or a second virtual machine server that allows overcommitment based on the score.

The present invention provides a technology that enables efficient use of the physical resources of a virtual machine server based on the frequency of virtual machine usage.

FIG. 1 illustrates an example of a virtual machine management system according to an embodiment of the present invention. FIG. 2 illustrates an example of a hardware configuration of a management device 10. FIG. 2 is a diagram illustrating an example of a functional block configuration of a management device 10. 13 is a flowchart illustrating an example of a processing procedure for selecting an area in which to place a virtual machine. 13 is a flowchart illustrating an example of a processing procedure for deleting a virtual machine. 13 is a flowchart illustrating an example of a process for migrating a virtual machine for which an increase in load is predicted to occur to a guarantee area.

The embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the same reference numerals are used to denote the same or similar configurations.

<System Configuration>
1 is a diagram showing an example of a virtual machine management system 1 according to this embodiment. The virtual machine management system 1 includes a management device 10, multiple virtual machine servers 20-1 to 20-4, and multiple virtual machines A to E that operate within the virtual machine servers 20-1 to 20-4. In the following description, when there is no need to distinguish between the virtual machine servers 20-1 to 20-4, they will be referred to as virtual machine servers 20. Furthermore, when there is no need to distinguish between the virtual machines A to E, they will be referred to as virtual machines.

The management device 10 and the multiple virtual machine servers 20-1 to 20-4 are connected via a wireless or wired communication network N and can communicate with each other.

The management device 10 manages the operating states of virtual machines A to E running on virtual machine servers 20-1 to 20-4, and performs operations such as selecting multiple virtual machine servers 20 on which to place virtual machines A to E. The management device 10 may also be referred to as a computer.

Virtual machine servers 20-1 to 20-4 are equipped with a hypervisor and can run one or more virtual machines. Virtual machine servers 20-1 and 20-2 are virtual machine servers 20 that do not allow overcommit, and in this embodiment, they are called the "guaranteed area" or "operation guaranteed area." On the other hand, virtual machine servers 20-1 and 20-2 are virtual machine servers 20 that allow overcommit, and in this embodiment, they are called the "best effort area."

Overcommit refers to allocating resources to virtual machines so that the total value of the resources allocated to the virtual machines exceeds the physical resources of the virtual machine server 20. For example, when memory and vCPUs (virtual CPUs) are allocated to virtual machines, it refers to allowing the total amount of memory and the total number of vCPUs allocated to all virtual machines to exceed the amount of physical memory and the number of CPU cores of the virtual machine server 20, respectively.

In general, it is rare for a virtual machine to always use the resources allocated to it to the maximum extent. Therefore, by allowing overcommit, it is possible to make effective use of the physical resources of the virtual machine server 20. However, if each virtual machine in a virtual machine server 20 that allows overcommit operates under a high load, the physical resources of the virtual machine server 20 may become insufficient, resulting in the disadvantage that the operation of the virtual machine may become unstable.

Therefore, in this embodiment, based on the usage frequency of the virtual machines, frequently used virtual machines are placed in the guaranteed area, and less frequently used virtual machines are placed in the best effort area. This makes it possible to efficiently use the physical resources of the virtual machine server.

<Hardware Configuration>
2 is a diagram showing an example of a hardware configuration of the management device 10. The management device 10 includes a processor 11 such as a central processing unit (CPU) or a graphical processing unit (GPU), a memory (e.g., a random access memory (RAM) or a read only memory (ROM)), a storage device 12 such as a hard disk drive (HDD) and/or a solid state drive (SSD), a network interface (IF) 13 for wired or wireless communication, an input device 14 for accepting input operations, and an output device 15 for outputting information. The input device 14 is, for example, a keyboard, a touch panel, a mouse, and/or a microphone. The output device 15 is, for example, a display, a touch panel, and/or a speaker.

<Function block configuration>
FIG. 3 is a diagram showing an example of a functional block configuration of the management device 10. The management device 10 includes a storage unit 100, an acquisition unit 101, a calculation unit 102, a placement control unit 103, and a prediction unit 104. The storage unit 100 can be realized using a storage device 12 provided in the management device 10. The acquisition unit 101, the calculation unit 102, the placement control unit 103, and the prediction unit 104 can be realized by the processor 11 of the management device 10 executing a program stored in the storage device 12. The program can be stored in a storage medium. The storage medium storing the program may be a non-transitory computer readable storage medium. The non-transitory storage medium is not particularly limited, and may be, for example, a storage medium such as a Universal Serial Bus (USB) memory or a Compact Disc Read-Only Memory (CD-ROM).

The memory unit 100 stores various data for managing the virtual machine server 20.

The acquisition unit 101 acquires statistical information regarding the operation of a virtual machine (first virtual machine) that is placed on a virtual machine server that does not allow overcommit (first virtual machine server, i.e., a guaranteed area).

The acquisition unit 101 also acquires the operation log of a virtual machine (second virtual machine) that is placed on a virtual machine server that allows overcommit (second virtual machine server, i.e., the best effort region).

The calculation unit 102 calculates a score indicating the usage frequency of the virtual machine from the statistical information acquired by the acquisition unit. For example, when the virtual machine is used to verify an application or the like, the usage frequency of the virtual machine may mean the percentage of a given time during which the virtual machine is used for verification. Note that a higher score may mean a higher usage frequency, or a higher score may mean a lower usage frequency. In this embodiment, the explanation is based on the premise that a higher score means a lower usage frequency. The time during which the virtual machine is used for verification may be an example of the usage frequency, and various other information such as the number or interval of connections from a specified client, and the number or interval of logins to a specified account may be used as the usage frequency.

The placement control unit 103 places the virtual machine (first virtual machine) to be placed in the guarantee area on a virtual machine server 20 (first virtual machine server) in the guarantee area or a virtual machine server 20 (second virtual machine server) in the best effort area based on the score calculated by the calculation unit 102.

In addition, when the score calculated by the calculation unit 102 is equal to or greater than a threshold value and it is determined that the virtual machine is used infrequently, the placement control unit 103 may move the virtual machine (first virtual machine) placed in the guarantee area to a virtual machine server 20 (second virtual machine server) in the best effort area.

In addition, when it is determined that the virtual machine is frequently used because the score calculated by the calculation unit 102 is less than a threshold value, the placement control unit 103 may continue to place the virtual machine (first virtual machine) placed in the guarantee area on the virtual machine server 20 (first virtual machine server) in the guarantee area.

In addition, when it is determined that the load of a virtual machine (second virtual machine) to be placed in the best effort region will increase in the future because the future load of the virtual machine (second virtual machine) predicted by the prediction unit 104 is equal to or greater than a threshold, the placement control unit 103 may place the virtual machine on a virtual machine server 20 (first virtual machine server) in the guarantee region.

In addition, when the period during which a virtual machine (second virtual machine) placed in the best effort region exists in the best effort region is equal to or longer than a threshold, the placement control unit 103 may store a snapshot of the virtual machine (second virtual machine) in the storage unit 100 and delete the virtual machine (second virtual machine) from the virtual machine server 20.

The prediction unit 104 predicts the future load of a virtual machine (second virtual machine) that is placed in the best effort region based on the operation log of the virtual machine. For example, the prediction unit 104 may predict the future load of the virtual machine using a learning model that is learned based on the relationship between the operation log and the future load of the virtual machine.

<Processing Procedure>
4 is a flowchart showing an example of a procedure for selecting an area in which a virtual machine is to be placed. The management device 10 repeats the procedure shown in FIG. 4 at predetermined intervals to periodically change the virtual machine server 20 in which a virtual machine is to be placed. The predetermined interval is not particularly limited, and may be a relatively long period, such as one week.

In step S10, the acquisition unit 101 acquires statistical information for each virtual machine from the virtual machine servers 20-1 to 20-4 in the guarantee area and the best effort area. The statistical information is information obtained by aggregating data related to the operation of virtual machines A to E over a predetermined period, and examples of such information include memory usage, CPU usage, disk size growth rate, Syslog size growth rate, and SSH (Secure Shell) log size growth rate. The predetermined period is not particularly limited, and may be the same as the period (e.g., one week) at which the management device 10 executes the processing procedure shown in FIG. 4. Note that the statistical information is not limited to these, and other data may be included as long as it is data related to the operation of the virtual machine. Furthermore, the statistical information is not limited to the case where all of these are used, and any data may be selected and used.

In step S11, the calculation unit 102 uses the acquired statistical information to calculate a score indicating the usage frequency for each virtual machine. The calculation unit 102 may calculate the score value by counting the number of items that are less than a predetermined threshold for each of the five items: memory usage, CPU usage, disk size growth rate, Syslog size growth rate, and SSH log size growth rate.

Specifically, the calculation unit 102 may calculate the score value according to the following steps 1 to 5. The initial score value is set to 0. The threshold value may be different for each item. The increase rate (%) means the increase rate from the point in time when the score was last calculated. For example, if the point in time when the score was last calculated is a predetermined period ago (e.g., one week ago), the increase rate of disk usage can be calculated by dividing the current disk usage by the disk usage from the predetermined period ago and multiplying the result by 100.
1. If memory usage is below the threshold, add 1 to the score.
2. If the CPU usage is below the threshold, add 1 to the score.
3. If the increase rate of disk usage is less than the threshold, add 1 to the score.
4. If the rate of increase in Syslog size is less than the threshold, add 1 to the score.
5. If the SSH log size growth rate is less than the threshold, add 1 to the score.

For example, if the memory usage and CPU usage of virtual machine A are less than the thresholds, but the other items are equal to or greater than the thresholds, the calculation unit 102 calculates that the score of virtual machine A is 2.

In addition, when calculating the score, weighting coefficients determined for each item may be taken into consideration. For example, the calculation unit 102 may calculate the score using weighting coefficients a to e according to the following steps 1 to 5.
1. If memory usage is less than the threshold, add 1×a to the score.
2. If the CPU usage is less than the threshold, add 1×b to the score.
3. If the increase rate of disk usage is less than the threshold, add 1×c to the score.
4. If the rate of increase in Syslog size is less than the threshold, add 1 x d to the score.
5. If the rate of increase in the SSH log size is less than the threshold, add 1×e to the score.

In step S12, the placement control unit 103 determines whether the score for each virtual machine is equal to or greater than a threshold. The threshold can be any value, but for example, if the score is expressed as a number between 0 and 5, the threshold may be set to 4 or greater. For virtual machines whose scores are equal to or greater than the threshold, the placement control unit 103 executes the processing procedure of step S13. For virtual machines whose scores are less than the threshold, the placement control unit 103 executes the processing procedure of step S14.

In step S13, the placement control unit 103 moves virtual machines whose scores are equal to or greater than the threshold from the guarantee area to the best effort area. Specifically, the placement control unit 103 copies various files constituting the virtual machine's actual state to virtual machine server 20-3 or virtual machine server 20-4 in the best effort area. After the copy is complete, the placement control unit 103 deletes various files from the guarantee area of the virtual machine copied to the best effort area from the virtual machine server 20 in the guarantee area where the virtual machine was placed. Note that no movement process is performed for virtual machines already in the best effort area, and the virtual machines continue to be placed in the best effort area as they are.

Here, the threshold value may be a fixed value. In this way, virtual machines whose usage frequency falls below a certain frequency can be reliably moved to the best effort area, making the criteria clear to virtual machine users and improving the governance of facility usage, for example by leading to notifications of voluntary termination of usage.

In step S14, the placement control unit 103 moves the virtual machines whose scores are less than the threshold from the best effort area to the guaranteed area. Specifically, the placement control unit 103 copies various files constituting the virtual machines to the virtual machine server 20-1 or virtual machine server 20-2 in the guaranteed area. After the copy is complete, the placement control unit 103 deletes various files from the best effort area of the virtual machine copied to the guaranteed area from the virtual machine server 20 in the best effort area where the virtual machine was placed. Note that no movement process is performed for virtual machines already in the guaranteed area, and the virtual machines continue to be placed in the guaranteed area as is.

Here, when deciding which virtual machines to place on the virtual machine server 20 in the guaranteed area based on the score calculated for each virtual machine, there is a risk that the total resource amount required by the virtual machines whose scores are below the threshold may exceed the virtual machine server 20 in the guaranteed area. If the virtual machine server 20 in the guaranteed area runs out of resources, the operation of the virtual servers in the guaranteed area becomes unstable. Therefore, when a certain amount of the resource amount (e.g., the amount of physical memory and the number of vCPUs) of the virtual machine server 20 in the guaranteed area is allocated to the virtual machine, the placement control unit 103 may notify the administrator in advance. For example, when 80% of the resource amount of the virtual machine server 20 in the guaranteed area is allocated to the virtual machine, the placement control unit 103 may notify the administrator. In this way, the administrator can take measures such as changing the threshold or increasing the resource of the virtual machine server 20 in the guaranteed area before the virtual machine server 20 in the guaranteed area runs out of resources.

The threshold value may also be a variable value. For example, assuming that virtual machines with the lowest scores are moved to the guarantee area in ascending order, the threshold value may be automatically calculated so that the total amount of resources allocated to each virtual machine to be moved to the guarantee area does not exceed the amount of resources possessed by the virtual machine server 20 in the guarantee area.

For example, assume that virtual machines A to E exist in the virtual machine management system 1, and that the scores of virtual machines A to E are 0, 1, 2, 5, and 5, respectively. Furthermore, when virtual machines A and B are moved to the guarantee area, the total amount of resources allocated to virtual machines A and B does not exceed the amount of physical resources of the virtual machine server 20 in the guarantee area. Furthermore, when virtual machines A, B, and C are moved to the guarantee area, the total amount of resources allocated to virtual machines A, B, and C exceeds the amount of physical resources of the virtual machine server 20 in the guarantee area. In this case, the placement control unit 103 may set the threshold to 2.

By doing this, even if it is not possible to place all virtual machines whose usage frequency exceeds a certain level in the guaranteed area, it is possible to prioritize placement of frequently used virtual machines in the guaranteed area, thereby ensuring the stability of frequently used virtual machines.

(Variation 1)
4, a virtual machine that is used infrequently is moved to a virtual machine server 20 in the best effort region. When this embodiment is applied to a virtual machine test environment, it is assumed that the virtual machine is tested in the guarantee region, and the virtual machine for which the test is completed is moved to the best effort region. In such an environment, virtual machines for which the test is completed may accumulate in the virtual machine server 20 in the best effort region, which may put a strain on the resources of the virtual machine server 20. Therefore, the management device 10 may delete the virtual machines that exist in the best effort region for a predetermined period of time.

Figure 5 is a flowchart showing an example of a processing procedure for deleting a virtual machine. The management device 10 may repeat the processing procedure shown in Figure 5 at predetermined intervals. The predetermined period is not particularly limited, but the management device 10 may repeat the processing procedure shown in Figure 5 at a longer cycle than the processing procedure shown in Figure 4, such as once a month or once every six months.

In step S20, the placement control unit 103 determines whether or not the period during which each virtual machine resides on the virtual machine server 20 in the best effort region is equal to or longer than a threshold. For example, the placement control unit 103 may determine the period during which each virtual machine resides on the virtual machine server 20 based on log data recorded on the virtual machine server 20 in the best effort region. If there is a virtual machine whose period during which it resides on the virtual machine server 20 is equal to or longer than the threshold, the placement control unit 103 proceeds to the processing procedure of step S21, and if there is no virtual machine whose period during which it resides on the virtual machine server 20 is equal to or longer than the threshold, the processing ends.

In step S21, the placement control unit 103 stores, in the storage unit 100 or the like, a virtual machine snapshot that constitutes the actual state of the virtual machine for a virtual machine that has been present on the virtual machine server 20 for a period of time equal to or longer than a threshold value. Note that a snapshot is data that records the latest operating state of a virtual machine, and includes, for example, all the latest data stored in memory and all the latest data written to disk.

In step S22, the placement control unit 103 deletes virtual machines that have been present on the virtual machine server 20 in the best effort region for a period of time equal to or longer than the threshold (i.e., deletes various files that constitute the virtual machine).

When an operation to restore a deleted virtual machine from a snapshot (restoration operation) is performed (for example, when a login is requested), the snapshot acquired before the deletion may be restored to the virtual machine server 20 in the best effort area. In this case, the latest snapshot related to the virtual machine may be used. In this way, the user can resume use of the virtual machine without being aware that the virtual machine has been deleted from the virtual machine server 20. In addition, when there are multiple snapshots related to the virtual machine, the snapshot to resume use may be selected by a predetermined method. The predetermined method may be, for example, selection by the user. In this way, the user can restore the virtual machine based on a snapshot at any time and resume use of the restored virtual machine. For example, when the environment is to be significantly changed from the time when the last verification was performed, the burden of the preparation work for verification may be reduced. In addition, the timing of the restoration is not limited to a request to login to the deleted virtual machine, and the user of the virtual machine may be able to operate it from a management screen or the like. Since restoration from a snapshot takes a certain amount of time, the verification work can be smoothly resumed by performing restoration in advance.

(Variation 2)
In the process shown in FIG. 4, a frequently used virtual machine in the best effort area is moved to the guarantee area based on the virtual machine's statistical information. However, in the process shown in FIG. 4, a frequently used virtual machine must operate in the best effort area before moving to the guarantee area. Therefore, depending on the usage mode of the virtual machine (for example, when verifying a high load state), resources may not be secured sufficiently, and the operation of the virtual machine may become temporarily unstable. Specifically, for example, if a virtual machine that was operating at a low load until the day before suddenly starts operating at a high load, resources may not be secured sufficiently in the best effort area, and the operation of the virtual machine may become unstable. Here, before a high load process is performed, for example, a process that does not itself impose a high load but is a precursor to a later high load process may be performed as preparation for the process, such as changing settings in the virtual machine, adding new software, or storing files used in the process. Therefore, when there is a precursor to a high load process, the virtual machine may be moved from the best effort area to the guarantee area in advance to avoid the operation of the virtual machine becoming temporarily unstable.

Therefore, if the management device 10 predicts that the load on a virtual machine in the best effort area will increase in the future, it may move the virtual machine to the guaranteed area in advance.

Figure 6 is a flowchart showing an example of a process for moving a virtual machine for which an increase in load is predicted to occur to a guarantee area. The management device 10 may repeat the process procedure shown in Figure 6 at predetermined intervals. The predetermined period is not particularly limited, but the management device 10 may repeat the process procedure shown in Figure 6 at a shorter cycle than the process procedure shown in Figure 4, such as every day. Furthermore, when executing the process procedure shown in Variation Example 2, step S14 of the process procedure in Figure 4 may be omitted.

In step S30, the acquisition unit 101 acquires operation log information of each virtual machine present in the virtual machine server 20 from the virtual machine server 20 in the best effort domain. The period for which the operation log information is acquired may be the same as the predetermined period for which the management device 10 repeats the processing procedure shown in FIG. 6. For example, when the management device 10 repeats the processing procedure shown in FIG. 6 every day, the operation log information acquired may be the most recent 24 hours.

In step S31, the prediction unit 104 predicts the future load of each virtual machine by inputting the operation log information of each virtual machine into a learning model that predicts the future load of the virtual machine.

Data included in the operation log information includes, for example, data on the number of accesses to the virtual machine, the amount of communication data, the number of logs indicating that the virtual machine has gone down (abnormally terminated), the frequency with which the swap space is used, the number of times a snapshot of the virtual server has been taken, the number of processes on the OS, the number of users of the OS, the number of times the OOM killer was activated, etc.

The learning model is a model generated by learning the relationship between operation log information and information indicating the future load of the virtual machine. The information indicating the future load of the virtual machine may be, for example, a load level indicating the load of the virtual machine one day from now. For example, the load level may be expressed as 1 to 10, with a higher load level indicating a higher load. In other words, the learning model may be, for example, a model that has been trained to output a load level when operation log information is input.

The learning model may also be a model that outputs information indicating the future load of a virtual machine by inputting the previous operation log information and the latest operation log information. In other words, the prediction unit 104 may predict the future load of each virtual machine by inputting the previous and latest operation log information of each virtual machine into a learning model that predicts the future load of the virtual machine. This makes it possible to more appropriately predict the future load of the virtual machine.

In step S32, the placement control unit 103 determines whether or not there is a virtual server whose future load is equal to or greater than the threshold among the virtual machines predicted in the processing procedure of step S31. If there is a virtual server whose future load is equal to or greater than the threshold, the placement control unit 103 proceeds to the processing procedure of step S33. On the other hand, if there is no virtual server whose future load is equal to or greater than the threshold, the placement control unit 103 ends the process.

In step S33, the placement control unit 103 moves the virtual servers whose future load is equal to or greater than the threshold from the virtual machine servers 20 in the best effort region to the virtual machine servers 20 in the guarantee region. The method of moving the virtual servers may be the same as the method described in step S14 of FIG. 4.

<Summary>
According to the embodiment described above, the management device 10 allocates a virtual machine to either the virtual machine server 20 in the guaranteed region or the virtual machine server 20 in the best effort region based on the usage frequency of the virtual machine. This makes it possible to efficiently use the physical resources of the virtual machine server.

In addition, the management device 10 saves a snapshot of a virtual machine that exists in the best effort region for a specified period of time and then deletes it. This makes it possible to prevent the resources of the virtual machine server 20 corresponding to the best effort region from being strained.

In addition, the management device 10 moves virtual machines that are expected to be heavily loaded in the future to the virtual machine server 20 in the guaranteed area in advance. This makes it possible to move the virtual machine to the guaranteed area before the load on the virtual machine actually becomes high, enabling the virtual machine to operate stably.

In addition, the technology related to this embodiment can contribute to achieving Goal 9 of the Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation and infrastructure."

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The flow charts, sequences, elements included in the embodiments, and their arrangements, materials, conditions, shapes, sizes, etc., described in the embodiments are not limited to those exemplified, and may be modified as appropriate. In addition, configurations shown in different embodiments may be partially substituted or combined.

1 Virtual machine management system, 10 Management device, 11 Processor, 12 Storage device, 13 Network IF, 14 Input device, 15 Output device, 20 Virtual machine server, 100 Storage unit, 101 Acquisition unit, 102 Calculation unit, 103 Placement control unit, 104 Prediction unit

Claims (9)

an acquisition unit that acquires statistical information about an operation of a first virtual machine arranged on a first virtual machine server that does not allow overcommit;
a calculation unit that calculates a score indicating a usage frequency of the first virtual machine from the statistical information;
a placement control unit that places the first virtual machine on the first virtual machine server or a second virtual machine server that allows overcommit based on the score;
A management device having the above configuration. The arrangement control unit is
If the score is equal to or greater than a threshold and it is determined that the virtual machine is used infrequently, the first virtual machine is migrated to the second virtual machine server;
If the score is less than a threshold value and it is determined that the usage frequency of the virtual machine is high, the first virtual machine is continued to be placed on the first virtual machine server.
The management device according to claim 1 . the placement control unit determines the threshold so that a total of requested resource amounts of the first virtual machines placed on the first virtual machine server does not exceed a resource amount of the first virtual machine server.
The management device according to claim 2 . The acquisition unit acquires an operation log of a second virtual machine arranged on the second virtual machine server,
a prediction unit that predicts a future load of the second virtual machine based on an operation log of the second virtual machine,
The arrangement control unit is
When it is determined that the load of the second virtual machine will increase in the future because the future load is equal to or greater than a threshold, the second virtual machine is allocated to the first virtual machine server.
The management device according to claim 1 . the placement control unit, when a second virtual machine is placed on the second virtual machine server and a period during which the second virtual machine exists on the second virtual machine server is equal to or longer than a threshold, stores a snapshot of the second virtual machine and deletes the second virtual machine from the second virtual machine server.
The management device according to claim 1 . the placement control unit restores the second virtual machine based on a snapshot of the second virtual machine in response to a restore operation being performed on the second virtual machine, the restore operation being an operation of restoring the virtual machine from a snapshot;
The management device according to claim 5 . the arrangement control unit, when there are a plurality of snapshots of the second virtual machine, restores the second virtual machine based on one snapshot of the second virtual machine selected by a predetermined method;
The management device according to claim 6. acquiring statistical information on an operation of a first virtual machine arranged on a first virtual machine server that does not allow overcommit;
calculating a score indicating a usage frequency of the first virtual machine from the statistical information;
distributing the first virtual machine on the first virtual machine server or a second virtual machine server that allows overcommit based on the score;
A management method executed by a management device, comprising: acquiring statistical information on an operation of a first virtual machine arranged on a first virtual machine server that does not allow overcommit;
calculating a score indicating a usage frequency of the first virtual machine from the statistical information;
distributing the first virtual machine on the first virtual machine server or a second virtual machine server that allows overcommit based on the score;
A program for causing a computer to execute the following.

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