In Azure Virtual Desktop (AVD), Host Pools and Session Host Pools are terms often used interchangeably, but they are crucial elements of the AVD infrastructure. However, they can have different connotations depending on the context. Let’s break down the two concepts:
Host Pools in AVD
- Definition: A Host Pool is a collection of virtual machines (VMs) that provide access to users in an Azure Virtual Desktop environment. A Host Pool is where you group together your virtual machines (either session hosts or personal desktops) based on user needs, configurations, and the intended workload.
- Role in AVD:
- A Host Pool can consist of multiple session hosts (VMs), which provide the virtualized desktop or application experience to multiple users.
- It can also contain personal desktops, where each user has their dedicated VM. This means you can use a Host Pool for both multi-session environments (session hosts) or single-session (personal desktops).
- Users are assigned to a Host Pool, and the pool is responsible for distributing users across the available session hosts in a round-robin or load-balanced fashion.
- Host Pools can be of two types:
- Pooled Host Pools (multi-session VMs where users are assigned randomly from the available VMs)
- Personal Host Pools (dedicated VMs for individual users).
- Key Features:
- Scalability: Host Pools can scale horizontally to meet user demand by adding more session hosts or personal desktops.
- Resource Management: You can control how resources are allocated and ensure users are distributed across available session hosts.
- Flexibility: Depending on the needs of the business, a host pool can be used to configure shared access to desktop environments or allocate dedicated virtual machines to users.
Session Host Pools
- Definition: A Session Host Pool is simply a Host Pool that specifically contains session hosts (VMs) that are running the Windows 10/11 or Windows Server multi-session OS, which allows multiple users to share the same VM.
- Role in AVD:
- A Session Host Pool is typically used in pooled environments, where many users need to share the same set of resources. The session hosts in a session host pool provide access to either full desktops or specific applications to multiple users.
- Session hosts within a session host pool are designed for multi-user scenarios, meaning that each VM in the pool can accommodate multiple users at the same time. The virtual machines host user sessions rather than providing dedicated virtual machines.
- Users are assigned to a specific session host in the pool, and the system manages their session on that VM.
- Key Features:
- Multi-Session: Each session host in a session host pool allows multiple users to log in and share resources, making it more cost-effective compared to providing each user a dedicated VM.
- Load Balancing: The session host pool typically uses load balancing or round-robin distribution to allocate users across the session hosts to ensure even resource usage.
Differences Between Host Pools and Session Host Pools
| Feature | Host Pool | Session Host Pool |
|---|---|---|
| Definition | A collection of virtual machines (either session hosts or personal desktops) that users are assigned to. | A specific type of host pool containing session hosts, which are VMs designed for multiple users to share resources. |
| User Assignment | Users are assigned to a host pool, which could be a personal desktop or session host pool. | Users are assigned to a session host within a session host pool (multi-user). |
| Type of VMs | Can contain both personal desktops (single-user) and session hosts (multi-session). | Contains only session hosts (multi-session VMs). |
| Usage Scenario | Used for both pooled and personal desktop scenarios. | Used specifically for multi-user access in pooled desktop environments. |
| Session Handling | Can be used for dedicated VMs (personal desktops) or shared sessions (session hosts). | Session hosts allow multiple users to connect to a single virtual machine (multi-session). |
| Scaling | Can scale with both personal desktops and session hosts based on the user’s needs. | Scales by adding more session hosts for more users, each hosting multiple user sessions. |
Conclusion
- Host Pools are the overarching resource group for your virtual machines in AVD, whether those VMs are session hosts (shared environments) or personal desktops (dedicated VMs for individual users).
- Session Host Pools are a specific type of Host Pool designed solely for multi-session environments where multiple users share the same session host (VM).
In essence, all session host pools are host pools, but not all host pools are session host pools. You can think of session host pools as a subset of host pools that are specifically configured to support shared, multi-user sessions.