> For the complete documentation index, see [llms.txt](https://docs.parallels.com/landing/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.parallels.com/landing/ras-reference-architecture/v19/deployment-scenarios/parallels-ras-deployment-scenarios/single-farm-with-rd-session-host-auto-scaling.md).
# Single Farm with RD Session Host Auto Scaling
This scenario can be implemented by an organization that needs to use single image management for RD Session Hosts and dynamic resource allocation for published applications and desktops.
For high availability, HALB Virtual Server (VS) should have a secondary HALB appliance, additional RAS Connection Broker and RAS Secure Gateway should be deployed. HALB Virtual Server (VS) is a virtual representation of the HALB appliances.
## **Installation Notes**
The components on the primary RAS Connection Broker are installed using the Parallels RAS installer (standard installation).
A new type of RAS Template adds support for an RD Session Host running in a guest VM where both the RAS Guest Agent and RD Session Host Agent are push-installed in the VM from the RAS Console.
An RD Session Host pool is assigned a RAS Template and is then used for publishing of applications and desktops.
RD Session Host creation, maintenance and deletion is done via the RAS Template.
An RD Session Host pool assigns RD Session Hosts on demand providing more resources on the workload increase and unassigns RD Session Hosts on the workload decrease.
HALB Virtual Server (VS) is configured with two HALB appliances.
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