balance RemoteApps and support servers with different published applications,
allowing a sum view of all the applications gathered from all servers in the farm to be
displayed to the user. This removes the need for all servers to have the same
applications. The Connection Broker is the brains of the virtual desktop environment
and communicates and controls the other components; it works particularly closely
with the RD Session Host in redirection mode that is required pre–Windows Server
2012, which is why they are frequently placed on the same OS instance. However,
when you start having more than 250 simultaneous connections, you may need to
consider breaking the roles onto separate servers.
Windows Server 2012 also enabled the Connection Broker to act as the initial entry
point for the incoming RDP connection, which previously required a dedicated RD
Session Host in redirection mode. This has removed the need to ever have an RD
Session Host in a redirection mode. Prior to Windows Server 2012, the RD Session
Host in redirection mode was required because when you have a large session host
server farm, to avoid users having to connect to different session hosts, the initial
entry point is always a designated session host that does nothing more than talk to the
broker and then redirect the RDP connection to the right RDP endpoint. This is the
same concept in a VDI environment; you still need an initial RDP connection point for
the RDP clients, which is exactly what the RDSH in redirection mode provides. It then
redirects the RDP client to the right client OS VM that will be providing their desktop
OS. By moving the functionality into the Connection Broker, you have one less
component to deploy.
The Connection Broker is also in charge of cleaning up the VDI instance after the user
logs off. This is achieved by the creation of a checkpoint, RDV_Rollback, when the VM
instance is created from the template, which is in a clean state before a user logs on.
Once a user logs off, the RDV_Rollback checkpoint is applied to the VM instance,
reverting the VM to the pre-user logon state and making it ready for the next logon. In
Windows Server 2008 R2, the RDV_Rollback checkpoint had to be manually created,
but this is done automatically in Windows Server 2012 and newer.
Typically, the Connection Broker uses a SQL Server cluster when deployed in a high-
availability configuration. However, Windows Server 2016 also adds support for using
Azure SQL Database, which reduces the number of roles and VMs required when
deploying an RDS solution in Azure. It’s also possible to use Azure AD Domain
Services for RDS in Windows Server 2016, which further reduces infrastructure
requirements as domain controllers are no longer required. Windows Server 2016 has
scale improvements for the Connection Broker, with tests up to 10,000 connections,
including burst storms that would have a significant percentage fail on Windows
Server 2012 R2 but now are all successful with Windows Server 2016.
RD Virtualization Host
The RD Virtualization Host role service is installed on any Hyper-V host that will be
participating in a VDI pool. It enables the Connection Broker to communicate with the