Session host virtual machine sizing guidelines
Whether you're running your session host virtual machines (VM) on Remote Desktop Services or Azure Virtual Desktop, different types of workloads require different VM configurations. The examples in this article are generic guidelines and you should only use them for initial performance estimates. For the best possible experience, you will need to scale your deployment depending on your users' needs.
Workloads
Users can run different types of workloads on the session host virtual machines. The following table provides examples of a range of workload types to help you estimate what size your virtual machines need to be. After you set up your virtual machines, you should continually monitor their actual usage and adjust their size accordingly. If you end up needing a bigger or smaller virtual machine, you can easily scale your existing deployment up or down in Azure.
The following table describes each workload. Example users are the types of users that might find each workload most helpful. Example apps are the kinds of apps that work best for each workload.
| Workload type | Example users | Example apps |
|---|---|---|
| Light | Users doing basic data entry tasks | Database entry applications, command-line interfaces |
| Medium | Consultants and market researchers | Database entry applications, command-line interfaces, Microsoft Word, static web pages |
| Heavy | Software engineers, content creators | Database entry applications, command-line interfaces, Microsoft Word, static web pages, Microsoft Outlook, Microsoft PowerPoint, dynamic web pages, software development |
| Power | Graphic designers, 3D model makers, machine learning researchers | Database entry applications, command-line interfaces, Microsoft Word, static web pages, Microsoft Outlook, Microsoft PowerPoint, dynamic web pages, photo and video editing, computer-aided design (CAD), computer-aided manufacturing (CAM) |
Single-session recommendations
Single-session refers to when there is only one user logged on to a session host virtual machine at any one time, such as when using personal host pools in Azure Virtual Desktop. For VM sizing recommendations for single-session scenarios, we recommend at least two physical CPU cores per VM (typically four vCPUs with hyper-threading). If you need more specific VM sizing recommendations for single-session scenarios, ask the software vendors specific to your workload. VM sizing for single-session VMs will likely align with physical device guidelines.
The following table shows examples of typical workloads:
| Workload type | vCPU/RAM/OS storage minimum | Example Azure instances | Profile container storage minimum |
|---|---|---|---|
| Light | 2 vCPUs, 8 GB RAM, 32 GB storage | D2s_v5, D2s_v4 | 30 GB |
| Medium | 4 vCPUs, 16 GB RAM, 32 GB storage | D4s_v5, D4s_v4 | 30 GB |
| Heavy | 8 vCPUs, 32 GB RAM, 32 GB storage | D8s_v5, D8s_v4 | 30 GB |
Multi-session recommendations
Multi-session refers to when there is more than one user logged on to a session host virtual machine at any one time, such as when using pooled host pools in Azure Virtual Desktop with the Windows 11 Enterprise multi-session operating system (OS). The following tables list the maximum suggested number of users per virtual central processing unit (vCPU) and the minimum VM configuration for each workload. If you need more specific VM sizing recommendations for single-session scenarios, ask the software vendors specific to your workload.
The following table shows examples of standard or larger user workloads:
| Workload type | Maximum users per vCPU | Minimum vCPU/RAM/OS storage | Example Azure instances | Minimum profile storage |
|---|---|---|---|---|
| Light | 6 | 8 vCPUs, 16 GB RAM, 32 GB storage | D8s_v5, D8s_v4, F8s_v2, D8as_v4, D16s_v5, D16s_v4, F16s_v2, D16as_v4 | 30 GB |
| Medium | 4 | 8 vCPUs, 16 GB RAM, 32 GB storage | D8s_v5, D8s_v4, F8s_v2, D8as_v4, D16s_v5, D16s_v4, F16s_v2, D16as_v4 | 30 GB |
| Heavy | 2 | 8 vCPUs, 16 GB RAM, 32 GB storage | D8s_v5, D8s_v4, F8s_v2, D8as_v4, D16s_v5, D16s_v4, F16s_v2, D16as_v4 | 30 GB |
| Power | 1 | 6 vCPUs, 56 GB RAM, 340 GB storage | D16ds_v5, D16s_v4, D16as_v4, NV6, NV16as_v4 | 30 GB |
For multi-session, we recommend limiting VM size to between 4 vCPUs and 24 vCPUs for the following reasons:
All VMs should have more than two cores: the UI components in Windows rely on using at least two parallel threads for some of the heavier rendering operations. For multi-session, having multiple users on a two-core VM will lead to the UI and apps becoming unstable, which lowers the quality of user experience. Four cores is the lowest recommended number of cores that a stable multi-session VM should have.
VMs should not have more than 32 cores: as the number of cores increase, the system's synchronization overhead also increases. For most workloads, at around 16 cores the return on investment gets lower, with most of the extra capacity being offset by synchronization overhead. You are likely to have more users from two 16 core VMs as opposed to one 32 core one.
The recommended range between 4 and 24 cores will generally provide better capacity returns for your users as you increase the number of cores. For example, let’s say you have 12 users sign in at the same time to a VM with four cores. The ratio is three users per core. Meanwhile, on a VM with eight cores and 14 users, the ratio is 1.75 users per core. In this scenario, the latter configuration with a ratio of 1.75 offers greater burst capacity for your applications that have short-term CPU demand.
This recommendation is true at a larger scale. For scenarios with 20 or more users connected to a single VM, several smaller VMs would perform better than one or two large VMs. For example, if you're expecting 30 or more users to simultaneously sign in within 10 minutes on the same session host with 16 cores, two eight-core VMs will handle the workload better. You can also use breadth-first load balancing to evenly distribute users across different VMs, rather than depth-first where a session host is saturated before using another one.
It's also better to use a large number of smaller VMs instead of a few large VMs because it's easier to shut down VMs that need to be updated or aren't currently in use. With larger VMs, you're more likely to have at least one user signed in at any time, which prevents you from shutting down the VM. When you have many smaller VMs, it's more likely you'll have some that don't have any users signed in. You can safely shut these unused VMs to conserve resources (either automatically using autoscale in Azure Virtual Desktop, or manually), making your deployment more resilient, easier to maintain, and less expensive.
General virtual machine recommendations
In addition to the base requirements to run your chosen OS, in Azure we recommend you use Premium SSD storage for your OS disk for production workloads that require a service level agreement (SLA). For more details, see the SLA for virtual machines.
Graphics processing units (GPUs) are a good choice for users who regularly use graphics-intensive programs for video rendering, 3D design, and simulations.. Azure has several graphics acceleration deployment options and multiple available GPU VM sizes. Learn more at GPU optimized virtual machine sizes. For more general information about graphics acceleration in Remote Desktop Services, see Choose your graphics rendering technology
B-series burstable VMs in Azure are a good choice for users who don't always need maximum CPU performance. For more information about VM types and sizes, see Sizes for Windows virtual machines in Azure and the pricing information on our Virtual Machine series page.
Test your workload
Finally, we recommend you use simulation tools to test your deployment with both stress tests and real-life usage simulations. Make sure your system is responsive and resilient enough to meet user needs, and remember to vary the load size to avoid surprises.
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