What Are Hyper-V Dynamic Memory Pros and Cons and How to Use It

Why do you need Hyper-V Dynamic Memory

Hyper-V Dynamic Memory, introduced in Windows Server 2008 R2 SP1, automatically balances the amount of physical memory for virtual machines on the server to improve restart reliability. Administrators can automatically adjust the physical memory of virtual machines based on application priorities to optimize performance and memory space.

Hyper-V dynamic memory vs fixed memory

In older versions of Hyper-V, you could only specify a fixed size of physical memory for virtual machines. What is the difference between Hyper-V dynamic memory and static memory?

🔰Allocation Methods:

Hyper-V dynamic memory can be automatically adjusted and flexibly allocated and reclaimed according to the virtual machine's operational needs, while Hyper-V static memory is pre-set at a fixed size and does not change automatically during operation.

🔰Resource Efficiency

Dynamic memory utilizes physical memory efficiently and can be flexibly allocated between virtual machines to avoid waste. Static memory can be wasted or underutilized.

🔰Impact on Virtual Machine Performance

Dynamic memory optimizes virtual machine application performance by allocating sufficient memory at peak demand and reclaiming it when demand drops. Static memory may limit performance due to under-allocation.

🔰Management Complexity

Dynamic memory is more complex to manage, taking into account configuration parameters and the impact on the application. Static memory management is simple and straightforward with a fixed size, but has some limitations.

After comparing the differences between Hyper-V dynamic memory and fixed memory, now let's discuss Hyper-V Dynamic Memory pros and cons further.

Hyper-V Dynamic Memory Pros and Cons

Hyper-V Dynamic Memory offers various advantages and disadvantages. If you want to know if it is suitable for you, please read this section carefully.

Advantages of Hyper-V Dynamic Memory

• Windows Server 2012 introduces smart paging, which improves the reliability of VM restart operations.
• Automatically reclaims memory from idle or low-load VMs and allocates it to VMs that need it, greatly improving resource utilization.
• Reduces wasted hardware resources and lowers the cost of hardware expenditures by accurately allocating memory.

Disadvantages of Hyper-V Dynamic Memory

• Enabling Hyper-V Dynamic Memory may cause problems with database applications, it is recommended to use compatible applications to avoid performance issues.
• When the VM is running or paused, you cannot resize the maximum and the minimum memory amount as well as modify the VM startup memory amount.
• Risk of overprovisioning computer physical memory in case you don’t keep track of memory allocation within your virtual environment.

Note: Database applications may have problems when Hyper-V Dynamic Memory is enabled. It is recommended that you use the applications that are compatible with Hyper-V Dynamic Memory to avoid any performance issues

How to use Dynamic Memory in Hyper-V [Best practice]

After learning Hyper-V Dynamic Memory pros and cons, you may have made your own decision. Hyper-V Dynamic Memory was integrated into Windows Server 2008 R2 Service Pack 1. If you want to use Hyper-V Dynamic Memory to improve virtual machine memory performance, please refer to the following practice.

Step 1. Enable Hyper-V Integration Services

In order to use Hyper-V Dynamic Memory correctly, you need to first enable Hyper-V Integration Services. Since the release of Windows Server 2016, you can install and update Hyper-V integration services via Windows Update. Hyper-V integration service must be enabled in the host and guests. The steps are as follows.

1. Open Hyper-V Manager, then click Action >> Insert Integration Services Setup Disk.

2. In guest virtual machine, select the DVD drive with the installation files. Right-click the DVD drive and select Install Hyper-V Integration Services.

3. The installation/upgrade of Hyper-V Integration Services will begin. Reboot your client/server.

4. Access to Hyper-V Manager Summary to check the version of Hyper-V Integration Services.

Step 2. Configure Hyper-V Dynamic Memory

Power-off your virtual machine before enabling Hyper-V Dynamic Memory.

1. Open Hyper-V Manager, select the virtual machine you want to configure. Then click Settings.

2. In the opened wizard, select Memory. You will see the multiple components such as RAM, Minimum RAM, Minimum RAM, Memory Buffer and Memory Weight. Let’s clear these components first, and configure them as you need.

Startup RAM: It is the minimum amount of physical memory that the VM can use at startup. It’s recommended to set up Strat RAM high enough to ensure the VM starts quickly.

Note: When installing or upgrading a virtual machine's operating system, ensure that the Startup-RAM value meets the minimum memory requirements of the operating system.

Minimum RAM: It’s the minimum amount of physical memory that should be assigned to the VM after it has started. You can reclaim the free and unused memory to the required VM until the minimum RAM value is reached (32 MB). When the virtual machine is running or paused, it’s impossible to increase the minimum memory, but you can decrease it.

Maximum RAM: It’s the maximum amount of physical memory that the VM can use. The range of Minimum RAM is from the assigned Startup RAM to 1 TB (1,048,576 MB). When the virtual machine is running or paused, it’s impossible to decrease the minimum memory, but you can increase it.

Memory Buffer: It is a portion of physical memory which is set aside for the VM based on its memory needs. By default, the memory buffer value amounts to 20%, but it can be set up to be as low as 5% and as high as 2000%. You can change the memory buffer value at any point, even while the VM is running.

Memory Weight: It determines the priority of the selected VM compared to other VMs on this host. In a production environment, some virtual machines have heavy workloads than others, so these virtual machines requiring higher performance should have a higher priority of additional memory than other general virtual machines.

One of the disadvantages of Hyper-V Dynamic Memory is that you need to monitor the memory usage constantly, otherwise it will overprovision RAM and completely run out of memory. You can use native monitoring tools or third-party software. For example, you can check the VM memory state through the host in Hyper-V Manager or the guest VM in Task Manager.

In addition, facing a large amount of enterprise data that needs to be backed up, try to choose a proper backup method that saves storage space. For example, flexible backup solution and automatic clean-up plan can effectively reduce the need for storage devices, thus reducing costs and time.

Memory saving way to backup Hyper-V virtual machine

AOMEI Cyber Backup is a professional backup software for virtual machines. It offers resilient backup strategies that can flexibly track the Hyper-V changed data. It allows you to schedule the backup and set up a cleanup policy to automatically delete unwanted backups. More benefits are as following.

Easy-to-use: Add all the VMs to the central console for backup and manage agentlessly. You can complete any operation via simple clicks.
Flexible backups: Easily backup entire virtual machine with full backup and offers incremental and differential backups for changed data.
Automate VM backup: Schedule tasks to backup unlimited virtual machines automatically and protect virtual machine continuously even though the VM is running.
Fast recovery: Instantly recover the whole VM to its precious state or restore it to another host without any complicated configuration and reinstallation.

*You can choose to install this VM backup software on either Windows or Linux system.

1. Click Backup Task >> Create New Task to start scheduling automatic backups (for example VMware ESXi Backup).

2. Select virtual machines and the destination to store the backups such as network or local location. For example, enter a NAS address and verify the identification to backup VMs to NAS.

3. Check Archiving backup versions to Amazon S3 and click Select to choose the added Amazon S3.

4. On Schedule window, for example, select full backup and incremental backup method, then set the backup frequency as weekly.

5. On Backup Cleanup window, specify the retention policy for each backup and choose to always retain the First full backup.

6. Click Start Backup.

Summary

We have discussed the Hyper-V Dynamic Memory pros and cons in this article. To put it simply, using dynamic memory correct can reduce memory consumption and costs, but it also has the cons of memory performance. Please make choice according to your own needs.