what is assigned memory in hyper v

Note: These Dynamic Memory fields can be changed while a virtual machine is running. Minimum RAM can be decreased, Maximum RAM can be increased and the Memory buffer can be either increased or decreased. The virtual machine will become of aware of the new limits without needing a restart.

Monitoring Dynamic Memory in Hyper-V

Dynamic Memory introduces variable amounts of RAM allocation on both the host and the virtual machines. So lets first take a look at how the RAM allocation looks from the hypervisor's perspective.

System Center Virtual Machine Manager

SCVMM gives the most complete view of the Dynamic RAM picture.

In this image, you can see there are varying amounts of assigned RAM to the three virtual machines.

The SCVMM view is great because it is complete and provides you with the total picture. It does however lag a little behind. The best place for more 'live statistics' are in the Hyper-V Management Console.

Hyper-V Management Console

The Hyper-V Management Console provides a simple and convenient real time view of the RAM assignment. It does not however give you the memory demand information. As such, is it not a great tool to determine the minimum baseline for your virtual machines.

Performance Monitor - Useful Performance Counters

By using Performance Monitor (Perfmon) on the host itself, you can get a very detailed live view of the Dynamic Memory picture. The key counters to use are:

Hyper-V Dynamic Memory Balancer

The Hyper-V Dynamic Memory Balancer counter gives you a view of how the host is doing from a memory perspective. In the image below, the host still has 66GB of RAM available to allocate based on demand. The current demand or 'pressure' from the virtual machines is 65. When the pressure gets to 100, the host is essentially out of RAM.

Hyper-V Dynamic Memory VM

The Dynamic Memory VM counter gives you a view very similar to what we have seen from the SCVMM and Hyper-V Management consoles.

One counter that is very useful here is the Guest Visible Physical Memory . This indicates how much RAM the virtual machine has visible, and it also indicates the high water mark for RAM demand. Perfmon also gives us the advantage of being able to track the RAM allocation on a graph.

Monitoring Dynamic Memory in the Virtual Machine

In a Dynamic Memory scenario, the virtual machine will be in one of three states.

Startup RAM before Dynamic

Less than Startup RAM

More than startup ram.

At startup, the virtual machine looks and behaves like a physical server with the Startup amount of RAM installed. The memory usage graph looks normal and from the Hyper-V console we can see that 4GB of RAM has been allocated.

A few minutes after the machine started, we notice a spike in the RAM usage. What has actually happened is not that the RAM usage has gone up, but that Dynamic Memory has started reducing the amount of physical RAM allocated to the machine. Since the virtual machine will never report less than the startup amount of RAM, it still reflects the 4GB.

You will notice however that usage is only at 70%. This is because of the memory buffer, if we increase or decrease the buffer size it will impact this percentage.

To simulate a sudden RAM increase, I am using a utility from Sysinternals called testlimit . When I demand an additional 2GB of RAM, the graph jumps. It then appears to level out even though the additional demand is still present. This is because more RAM has been allocated by the host.

When the additional 2GB demand is removed again, the graph drops.

Once the pressure normalises, the virtual machines goes back to only consuming the usual 2GB of physical RAM.

When I demand an additional 4GB of RAM above the baseline, it exceeds the Startup RAM. The virtual machine is then allocated additional physical memory from the host. At this point the installed memory count also goes up.

Note that even after the load has been removed and Dynamic Memory has released, the physical memory and the installed memory still reports 6GB. As covered earlier, the visible amount of RAM will never drop below the highest allocated amount.

Below is a 20 second interval Perfmon graph showing a trace of both physical memory and pressure from the host's perspective.

You can see that when the pressure is raised, the RAM amount increases almost immediately. Once the RAM is allocated, the pressure drops a little. When the load is removed, the pressure goes way down, and when the pressure stays low for a few minutes, the RAM allocation drops. At this time, the pressure goes back to the standard count of about 60.

So how much memory is actually allocated and used?

This still leaves the question of how much memory is actually allocated and used? For this information, you can use another tool from Sysinternals called RAMMap .

In RAMMap, the counter to look for is called Driver Locked . At startup there is basically no RAM locked. Once Dynamic Memory steps in and releases the physical RAM, you can see the Driver Locked amount increases. At this stage the Total still stays the same.

When we bump the load up again, the Total increases. Once we terminate the process, the RAM moves to being unused.

When Dynamic Memory releases the physical RAM, the unused amount is now moved to Driver Locked.

It is important to remember that the Driver Locked amount is an artificial lock on RAM that does not really exist for the virtual machine since it is not backed by any physical RAM from the host.

Making use of Dynamic RAM in Hyper-V is a great way to maximise the hardware you have available. Having a proper understanding of what the actual demands of your virtual machines are can help you tailor its RAM settings.

Realistic figures should be used when specifying the Startup and Minimum RAM amounts. If these are too low you will inevitably invoke the dynamic addition and removal of RAM all the time. Although this is not a problem, it does carry some overhead.

When looking at memory utilisation on the virtual machine it is important to remember the context in which it exists, just because it indicates a high percentage of RAM utilisation, does not mean it is consuming that amount of physical RAM.

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Understanding Hyper-V CPU Usage (Physical and Virtual)

How to Enable Dark Mode in Fortinet FortiGate (FortiOS 7.0)

Memory Management, Requirements and Usage in Hyper-V

Table of contents.

Memory is the most precious resource in the typical virtualization host. It cannot be shared among virtual machines. The computing costs to compress or de-duplicate it are so prohibitive that neither is feasible.

Virtual machine density relies heavily on the amount of installed physical memory, but the financial cost of memory escalates quickly with higher chip capacities. Proper memory planning is absolutely essential to a successful Hyper-V deployment. In this article I’ll explain the concepts of memory in a Hyper-V environment to give you the necessary background to make those plans.

Hyper-V’s Memory Operations and Requirements

A hypervisor’s primary purpose is to control access to hardware, and that includes memory. It walls off the memory assigned to each virtual machine in such a way that the virtual machine “sees” its memory in the same way a physical machine views its memory. It is completely unable to access anything other than what Hyper-V assigns to it.

The technique that Hyper-V uses to achieve this is address translation . As you may recall from the introductory article on Hyper-V , the Hyper-V server role benefits greatly from hardware-based translation, called Second Level Address Translation, although it can perform it in software if necessary. 2012 R2 is the last server version that will include this software capability; Client Hyper-V has never had it. The following diagram provides a conceptual illustration of address translation:

The guest operating system of each virtual machine believes that its memory address space starts at 0 and counts upward to encompass all available memory. When it passes requests for memory access through its CPU, the request is translated into the physical memory address behind the scenes.

Hyper-V’s memory assignment and tracking activity is not without its own costs. Hyper-V itself needs about 300 megabytes of memory for its own process. For each virtual machine, any memory amount up to the first megabyte requires 32 megabytes of overhead. Every gigabyte past the first incurs another 8 megabytes of overhead. All of this is in addition to the 512 megabytes that the management operating system requires (it will often use less, but it cannot be pre-estimated with any level of accuracy).

This means that the absolute minimum amount of memory that you should expect your physical host to be unable to utilize for virtual machines is 1 GB. In practice, it is commonly observed that other processes in the management operating system require even more memory to be set aside. For a typical Hyper-V host, expect about 2 GB to be necessary just to run Hyper-V and the management operating system. For a high memory host that will serve a high number of virtual machines, it is wise to plan for as much as 4 GB for the system and overhead.

Hyper-V’s management operating system uses a page file just like any other installation of Windows. However, its automatic process is likely to result in an inappropriate size. The next section discusses this issue.

Hyper-V and the Page File

In earlier versions of Hyper-V, the management operating system’s page file was automatically set by Windows to be at or above the same amount as system memory. Since a virtualization host typically has a great deal of memory, this was causing automatic creation of page files that were dozens or even hundreds of gigabytes in size. This is completely unnecessary for a Hyper-V host.

Unlike some other hypervisors, Hyper-V does not provide memory paging operations for its guests except under very rare, specific conditions. In those situations, it does not use the management operating system’s page file. Therefore, creating a large page file is wasteful as most memory contents on a Hyper-V system will never be paged to disk in any way that the management operating system or hypervisor will be involved with.

The default page file allocation system in 2012 and later is superior to earlier versions, but still often results in very large page file sizes. If the default allocation is not causing disk space starvation on your host, the recommendation is to leave it set to System Managed . Even though it’s not the most efficient use of space, it does allow the management operating system to respond to extenuating circumstances with less administrative intervention. Such situations are rare, so if reclaiming the space is of meaningful benefit, then do so.

Virtual Machine Memory

The bulk of the memory in your hosts will be assigned to the virtual machines. The bulk of a Hyper-V administrator’s resource management time is often focused on memory balancing. The best approach is to develop a habit of providing the minimal acceptable level of memory to each virtual machine and only increasing it after need has been demonstrated.

The simplest distribution method is to use static memory (sometimes called fixed memory ). This ensures maximum compatibility at the immediate expense of virtual machine density. It can also affect virtual machine mobility. In order to move a virtual machine from one host to another, the destination must have available capacity for that virtual machine; the less memory assigned to that virtual machine, the more likely it is to fit. Static memory is required for a number of server applications, such as Microsoft Exchange Server, as they allocate memory on the basis of what is available.

A more complicated method that leads to higher densities is Dynamic Memory . This technology operates by interacting with the memory manager inside guest operating systems to gauge what amount of memory the services and applications are requesting. If the requested amount exceeds the assigned amount, Dynamic Memory can assign more to that virtual machine (up to 1 terabyte or a lower administrator-defined limit). If other virtual machines increase their demand such that the total exceeds what is physically available, Dynamic Memory can determine if any guests have a lower demand than what is assigned to them and use a balloon driver to reclaim the excess for redistribution.

The following image illustrates a conceptual usage of Dynamic Memory for a single virtual machine:

The amount of memory that the virtual machine believes it has starts at the Startup level. It can increase, but it can never decrease. Instead, the hypervisor calls on the balloon driver to expand its memory request to the guest’s memory manager. The guest believes that it has some control over the memory consumed by the balloon driver but that a local process is using it; in truth, it is controlled by the hypervisor; it might be assigned to a virtual machine or left in the host’s pool. What the diagram doesn’t show is that the balloon driver is only activated when there is memory contention. If a virtual machine’s demand is reduced and no other virtual machine requires an increase, Dynamic Memory does not activate.

There are several things about Dynamic Memory to take note of:

We’ve covered Dynamic Memory across several posts on our blog. You can find them here if you’d like to dive deeper into the subject:

NUMA in Hyper-V

NUMA (non-uniform memory access) is a technology used to maintain maximum performance in multi-processor environments. If your system has only a single physical processor, NUMA is not a concern. In multi-processor systems, only a very few applications are sensitive enough to memory performance issues that NUMA is something to worry about.

The contrast to NUMA is the older SMP design (symmetric multi-processing). In much older systems, the memory controller was a component that resided on the motherboard. Its purpose is to broker all connections to memory and to keep the contents of memory in a consistent state. When a CPU needed to access memory, a request would be sent to the memory controller. In multi-processor systems, all requests would be handled through the same controller. It would handle each request in a round-robin fashion which lead to an even distribution of process memory across available memory banks, hence the “symmetric” nomenclature.

Over time, memory controllers became integrated onto the CPU to address various performance and reliability issues. In modern multi-socket systems, physical memory banks are assigned to particular sockets. If that socket has a CPU, then those banks are handled by its memory controller. If a thread running on a different physical CPU needs to access memory, then it must go through the CPU that contains the owning memory controller. If the host is in SMP mode (called node interleaving on some systems), then threads will be evenly distributed across the memory banks by working through controllers on other CPUs.

If NUMA is enabled (which means that node interleaving is disabled on systems using that name), then the system tries to ensure that threads running on any given physical processor are assigned memory owned by that processor’s memory controller. This improves performance for applications that do not allocate memory amounts greater than the maximum size of a NUMA node. It should be reiterated that the performance difference is very small and very few services or applications are sensitive enough to the difference for it to be of concern.

Hyper-V does have the ability to project NUMA topology into virtual machines that are using fixed memory allocation. Use the memory settings in Hyper-V Manager or PowerShell to control it. The projected topology does not need to match that of the host. Do not change these settings unless you have a very clear understanding of NUMA and its effects. It is much easier to hinder performance than to improve it. As mentioned in the previous section, NUMA is not projected into guests configured for Dynamic Memory as guest NUMA cannot be changed on the fly.

Working with Memory

The easiest way to work with memory for a single Hyper-V guest is to use Hyper-V Manager as shown in the earlier article on Virtual Machine settings . The PowerShell cmdlet to modify memory for a virtual machine is Set-VMMemory. Its documentation can be found here . Host NUMA must be enabled in the system BIOS. Once enabled, there is nothing else to configure at the host level. You can view its status using PowerShell. The related cmdlets are Get-VMHostNumaNode and Get-VMHostNumaNodeStatus .

Now that you’ve gained an understanding of the challenges around memory and how Hyper-V handles it, you have the foundational knowledge to properly plan memory capacity for your deployment.

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How to Configure VM Memory

How much memory do I need to give this virtual machine (VM), and how do I do that? That very question has kept even the best IT pros up at night. But it's time we change that. We need to band together and attack our IT anxieties head-on.

Today we are going to help you learn how to configure VM memory , how much memory you need to give to VMs, and how not to create memory performance issues in Hyper-V.

An Overview of How to Configure VM Memory

Understanding how to assign memory to a virtual machine is an essential skill for sysadmins who want to make their hardware more effective and efficient. In this video, James Conrad shows you how to configure and allocate memory for a virtual machine — and why it's essential to allocate the appropriate amount of memory for your applications.

How do I Configure VM memory?

Configuring virtual memory allocation in Hyper-V is an easy process. So, without further fanfare, let's get into it.

First, launch the Hyper-V Manager in Windows. The Hyper-V Manager is the primary administration snap-in component for the Windows OS. Note that these instructions are for Windows 10 Pro, Windows 11 Pro, and recent versions of Windows Server with a user interface. Bare versions, or the base version of Hyper-V, do not include any user interfaces and must be configured via the command line. In that case, the Hyper-V Manager can be used from another Windows machine to manage Hyper-V remotely instead, but that is an IT tragedy for a different story.

After opening Hyper-V Manager, select your VM cluster from the side panel.

Next, locate the VM that you need to edit. Depending on your environment, you may have lots of virtual machines. If this is a home lab, there's a good chance you only have a few VMs on hand.

After finding the virtual machine in question, right-click the VM and choose settings. This will launch the settings panel that has various settings for Hyper-V VMs. The settings that are accessible from this panel are only standard settings. There are a ton more options available if you configure Hyper-V through PowerShell .

In the settings pane, choose Memory. Pay attention to the first setting in the memory tab. This is where you set the target amount of RAM assigned to your VM. Adjust this setting and click Apply.

Adjusting the memory assigned to a VM in Hyper-V is as simple as that. We're not done, however. Nothing in IT is ever that easy, is it?

What is Dynamic Memory in Hyper-V?

Most hypervisors have something called dynamic memory, including Hyper-V. So, here's where life gets tricky. If you look under the Dynamic Memory area of the Hyper-V settings window, you'll notice a minimum and maximum setting. Hyper-V can adjust the amount of memory a VM uses in real-time. But, of course, things get muddy here.

The first setting you changed assigned the amount of memory a VM uses on startup. This is akin to a cold start on your computer. If you assign a VM 8Gb of memory, your VM will claim and use 8Gb of memory on startup. If you adjust the min and max memory settings to 8Gb, your VM will constantly claim and use exactly only 8Gb of physical memory.

That's not the wisest idea, however. Windows will use unused memory as cache space, but we don't need that in the VM world. We want to utilize our hardware to its fullest extent. Using unused memory for application cache is typically at the bottom of our list.

So, we'll set the min and max memory more appropriately. For instance, our minimum amount of memory might be set to 2Gb. A typical office-use PC typically doesn't drop below 2Gb of memory usage. We might also set the max memory to 16Gb. We don't want our end-users to keep opening apps and use all the physical memory a server is sharing between multiple VMs.

What is Memory Buffer in Hyper-V?

Next, there is an option for a memory buffer. Since Hyper-V needs to adjust the memory allocated and used by each VM constantly, sometimes it's good to give a specific VM a bit of buffer space.

For instance, if this VM is a mission-critical VM, you might want to give it a 30% buffer. That means the hypervisor will assign 8Gb of memory to the VM plus 30% just in case it needs it. That way, other greedy VMs don't come and take that valuable RAM space from our mission-critical virtual machine.

What is Memory Weight in Hyper-V?

Finally, we have a setting for weight. This setting states where this VM falls in the pecking order. If the VM is super important, it gets a higher weight. That way, the hypervisor knows whom to service first. VMs with a lower weight are considered second-class citizens and only get resources after VMs with a higher weight are taken care of first.

Wrapping Up

Assigning the correct amount of memory to your virtual machines is very important. The entire point of virtualization is to utilize more hardware while reducing TCO in the enterprise space. Virtualization is also a valuable tool for home labs. Nonetheless, if you assign too much memory to each VM, you will not be able to utilize your server hardware as best as possible. If you give too little memory to your VMs, you will have performance issues. Either way, you are going to have a bad time.

So, learn how to implement Hyper-V the right way. Hyper-V is a fantastic tool that also happens to be free. It's included with Pro versions of Windows, Server versions of Windows, and as a standalone bare-metal hypervisor.

After you learn how to get those VMs up and running, learn how to use PowerShell with Hyper-V and become a virtualization god/ess. You can do amazing things with Powershell and Hyper-V, including automating your entire VM environment and enabling sunset settings like RemoteFX (something that must be done through the command line).

Finally, learn how to cluster and replicate VMs in Hyper-V. All enterprise environments want both high availability as well as redundant systems.

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Hyper-V Dynamic Memory: Startup memory vs Minimum Memory

When I setup a VM, I can set Min RAM, Max RAM, and Startup RAM. I know what they each mean but not how they interact with each other.

If I have a VM that needs a lot of memory when it boots up because it has to start up a bunch of services and processes, but then it doesn't need as much once it's running under normal conditions, I can set the Startup RAM to be higher than the Minimum RAM.

E.g. Startup 8 Gigs, Minimum 2 Gigs, Maximum 16 Gigs.

At boot, the VM gets 8 Gigs of RAM. Once it's done starting up it could drop to as low as 2 or increase to as much as 16 depending on the demand of the VM.

The main question I have is, how long does Startup RAM remain active before it starts the Dynamic usage.

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Start Up RAM will be active until the VM boots up ,once server boots up , it will use Minimum RAM. Depending on the usage, VM will start consuming RAM to the value of MAX RAM (if demand is there)

If more RAM is required after the MAX RAM is reached, memory buffer comes into picure.

Just read the below artice and all your questions will be answered. :)

I get that. But what defines when the VM has "booted up"? Is it a time? (e.g. startup memory is active for 2 minutes) Is it when a certain service or process starts? That's what we're trying to figure out.

If I have a plain VM with Server 2016 and nothing else installed, if I set Startup RAM to 16 Gigs and Minimum to 2 Gigs, when I turn it on, it gets 16. At what point will it stop using the Startup value and switch to the Min/Max values?

Kelemvor wrote: What defines when the VM has "booted up"? Is it a time? (e.g. startup memory is active for 2 minutes) Is it when a certain service or process starts?

Without being 100%, I guess it's up to the hypervisor (hyper-v) to determine if the host really needs the ram and is 'successfully and completely booted.

The startup RAM is the amount of physical RAM that will be allocated to the virtual machines at startup. Regardless of what the actual RAM demand is, the host will reserve this for the virtual machine. From the virtual machine’s perspective, the amount of visible RAM will never drop below the Startup RAM amount.

Once the VM boot is complete and the hypervisor started , it will try to use the amount of RAM configured as the minimum RAM. How long that takes for this process depends and as said, seems to be determined by the hypervisor ( e.g. by guest / integration services that run on the VM and provide the hypervisor with feedback)

https://www.veeam.com/blog/hyper-v-dynamic-memory-managing-vm-ram.html Opens a new window

Kelemvor wrote: I get that. But what defines when the VM has "booted up"? Is it a time? (e.g. startup memory is active for 2 minutes) Is it when a certain service or process starts? That's what we're trying to figure out. If I have a plain VM with Server 2016 and nothing else installed, if I set Startup RAM to 16 Gigs and Minimum to 2 Gigs, when I turn it on, it gets 16. At what point will it stop using the Startup value and switch to the Min/Max values?

When a server starts up, it will not really start up that many applications or "heavy" services. Even if it does, there is the paging to assist with RAM operations especially when your are talking about 2GB RAM vs 16GB RAM....

The main question is where do you see the RAM spike to 16GB or max and how long does it lasts ?

This topic has been locked by an administrator and is no longer open for commenting.

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Hyper-V Dynamic Memory Pros and Cons | Best Practice

When using virtual machines, memory is easy to be consumed fast. How to reduce memory consumption? In Hyper-V, enabling Dynamic Memory is an efficient solution to reclaim the unused memory to the required virtual machines automatically.

Why do you need Hyper-V Dynamic Memory

Hyper-V Dynamic Memory was originally introduced in Windows Server 2008 R2 with SP1. It is designed to automatically balance the amount of physical memory occupied by virtual machines running on a server, improving the reliability of restart operations. Administrators can automatically adjust the amount of physical memory for virtual machines based on the application priority, thus optimizing application performance and memory space.

In older versions of Hyper-V, you could only specify a fixed size of physical memory for virtual machines. But virtual machine requires more memory at startup than its steady state, so two scenarios often occurred. One is that the allocated memory is exhausted and the virtual machine needs to be shut down and resized. The other is that the virtual machine is allocated too much memory than it actually needs, which cannot be reclaimed after booting, resulting in wasted resources.

Now let's discuss Hyper-V Dynamic Memory pros and cons further.

Hyper-V Dynamic Memory advantages and disadvantages

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

1. Improves the reliability of start-up operations. In Windows Server 2012, Smart Paging was introduced to ensure the reliable virtual machine restart operations.

2. Improve resource utilization. Dynamic memory makes full use of memory resources by automatically reclaiming free or low-load VM memory and allocating it to Hyper-V VMs that requires more memory.

3. Reduce hardware spending. Allocating memory to each virtual machine accurately reduces the waste of resources on hardware, thus saving costs.

Disadvantages of Hyper-V Dynamic Memory

Hyper-V Dynamic Memory also has drawbacks that can negatively impact VM memory performance.

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

1. When Hyper-V Dynamic Memory is enabled, issues with database applications may occur. It is recommended that you use applications that are compatible with Hyper-V Dynamic Memory to avoid any performance issues.

2. 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.

3. Risk of overprovisioning computer physical memory in case you don’t keep track of memory allocation within your virtual environment.

advantages and disadvantages of Hyper-V dynamic memory

Best practice to use Dynamic Memory in Hyper-V

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.

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.

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.

There is a formula to calculate the memory buffer.

Amount of memory buffer = how much memory the virtual machine actually needs / (memory buffer value / 100).

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

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

5. Click Start Backup .

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.

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IMAGES

How to list all VMs and assigned memory on the Hyper-V cluster.
Free Up Memory for Hyper-V Guests
What is Microsoft Hyper-V? (Includes Key Resources!)
Hyper-V Dynamic Memory for Ubuntu 15.10
How to list all VMs and assigned memory on the Hyper-V cluster.
How to Run Hyper-V in a Virtual Machine with Nested Virtualization?

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02- Hyper-V Management
Hyper-V Part 5
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Shape Memory Alloys Can Lift Rocks
Hyper v compute platform is not enabled
RAM settings in Hyper-V

COMMENTS

Full Overview of Hyper-V Dynamic Memory Best Practices
This Hyper-V Dynamic Memory value defines the minimum amount of physical memory a selected VM can use during its startup. Startup RAM should be
Hyper-V Dynamic Memory Overview
To provide a reliable restart experience for the virtual machines configured with less minimum memory than startup memory, Hyper-V uses Smart
Configure at least the required amount of memory for a virtual
Increase memory using Hyper-V Manager · Open Hyper-V Manager. · From the list of virtual machines, right-click the one you want, then click
Managing VM RAM better with Hyper-V dynamic memory
Keep in mind that to enable or disable dynamic memory, the VM must be powered off at the moment. So once you create a VM or edit an existing one
Understanding Hyper-V Dynamic Memory (Dynamic RAM)
This is the amount of physical RAM that will be allocated to the virtual machines at startup. Regardless of what the actual RAM demand is, the
Memory Management, Requirements and Usage in Hyper-V
Hyper-V itself needs about 300 megabytes of memory for its own process. For each virtual machine, any memory amount up to the first megabyte requires 32
Hyper-V Dynamic Memory Configuration with Best Practices
With dynamic memory, the Hyper-V host monitors the memory usage of the guest operating system and then can dynamically adjust the memory
How to Configure VM Memory
Most hypervisors have something called dynamic memory, including Hyper-V. So, here's where life gets tricky. If you look under the Dynamic
Hyper-V Dynamic Memory: Startup memory vs Minimum Memory
The startup RAM is the amount of physical RAM that will be allocated to the virtual machines at startup. Regardless of what the actual RAM
Hyper-V Dynamic Memory Pros and Cons
Hyper-V Dynamic Memory was originally introduced in Windows Server 2008 R2 with SP1. It is designed to automatically balance the amount of