Resource Based & Round Robin Load Balancing

Load Balancer is designed to balance RDS and VDI provider connections made from Parallels Clients.

The following types of load balancing methods are available:

• Resource Based. Distributes sessions to servers depending on how busy the servers are. Therefore a new incoming session is always redirected to the least busy server.
• Round Robin. Redirects sessions in sequential order. For example, the first session is redirected to server 1, the second session is redirected to server 2, and the third session is redirected to server 1 again when there are two RD Session Hosts in the Farm.

Both methods are explained in this and the following subsections.

Load Balancing options can be configured from the Load Balancing category in the RAS Console.

Enabling Resource Based Load Balancing

Load balancing is enabled by default when more than one server is available in a Site. The resource-based load balancing is the default method.

To switch back to resource-based from round-robin, select Resource Based in the Method drop-down list.

Configuring Resource Counters

Resource-based load balancing uses the following counters to determine if a server is busier than the other/s and vice versa:

• User sessions. Redirect users to a server with the least number of sessions
• Memory. Redirect users to the server with the best free/used RAM ratio
• CPU. Redirect users to the server with the best free/used CPU time ratio

When all of the counters are enabled, the RAS Load Balancer adds the counter ratios together and redirects the session to the server with the most favorable combined ratio.

To remove a counter from the equation, clear the checkbox next to the counter name in the Counters section.

Round Robin Load Balancing

Round-robin load balancing redirects sessions in sequential order. For example, with two RD Session Hosts in the Farm, the first session is redirected to server 1, the second session is redirected to server 2, and the third session is redirected to server 1 again. To enable round-robin load balancing, select Round Robin in the Method drop-down list.

Session Options

Reconnect to Disconnected Sessions. Enable this option to redirect incoming user sessions to a previously disconnected session owned by the same user.

Reconnect sessions using client’s IP address only. When reconnecting to a disconnected session, the Parallels RAS will match the username requesting reconnection with the username of the disconnected session to match the sessions. With this option enabled, Parallels RAS will determine to which disconnected session to reconnect the session by matching the source IP address.

Limit user to one session per desktop. Enable this option to ensure that the same user does not open multiple sessions. Please note that for this option to work, your RD Session Hosts must also be configured to restrict each user to a single session. In Windows Server 2008, you need to enable the "Restrict each user to a single session" option in Remote Desktop Session Host Configuration. In Windows Server 2012(R2), it's the "Restrict Remote Desktop Services users to a single Remote Desktop Services session" option in Local Group Policy \ Remote Desktop Services \ Remote Desktop Session Host \ Connections.

Disable Microsoft RD Connection Broker. If this option is enabled, the Microsoft RD Connection Broker will not interfere with the RAS brokering done by the RAS Publishing Agent if it is installed. Please note that this option will only work with Windows Server 2012 and above.