Product Documentation

Manage Server OS machine server load

Mar 08, 2013

Load Management measures the server load and determines which server to select under the current environment conditions.

When a user logs on to a Server OS machine, Load Management assigns the user to the server that is best suited to handle the request. This selection is based on:

  • Server maintenance mode status
  • Server load index, which is a number that represents the aggregated load, based on various measured parameters including CPU usage, memory usage, and disk usage. Load Indexes are calculated based on a formula, called the Load Evaluator.
  • Concurrent logon tolerance setting, which is the allowed number of concurrent requests to log on to the server.

Maintenance mode

The XenDesktop server maintenance mode status and the Microsoft Windows Remote Desktop Connection (RDC) setting affect whether the Server OS machine is considered in load management.

Maintenance mode is on if any of the following occur:

  • XenDesktop server maintenance mode is set to On
  • RDC is set to Don’t allow connections to this computer
  • RDC is not set to Don’t allow connections to this computer, and the Remote Host Configuration User Logon Mode setting is one of the following:
    • Allow reconnections, but prevent new logons
    • Allow reconnections, but prevent new logons until the server is restarted

The Server OS machine is only considered for load balancing when maintenance mode is off.

Server load index

A server's load index determines how likely a server delivering Server OS machines is to receive connections. It is the combination of:

  • The number of sessions
  • Settings for performance metrics such as CPU, Disk, and Memory use

You can configure these load evaluators through the Load Management policy settings, as described in Load Management policy settings.

You can monitor this index through:

  • Studio Search feature

    By default the Server Load Index column is hidden. Include this attribute in the display:

    1. Select a machine.
    2. Right-click a column heading and then choose Select Column.
    3. In the selected machine tab, scroll right to display the Machine attribute column for Server Load Index.
    4. In the Machine folder, select Server Load Index.

      You can alternatively view load index information by using the PowerShell SDK Get-BrokerMachine. See for SDK information, see About the XenDesktop SDK.

      Note: A Server Load Index value of 10000 indicates that the server is at full load. If no other servers are available in the Site, users may receive a message that the desktop is currently unavailable when they launch a session.
  • Director — See the Director documentation for information about monitoring this index.

Concurrent Logon Tolerance setting

You can control the number of pending logons a server delivering Server OS machines can concurrently accept by setting the Concurrent Logon tolerance. This helps avoid server performance problems.

The Concurrent Logon Tolerance setting is equivalent to Load Throttling in XenApp.

If all servers are at or higher than the Concurrent Logons Tolerance setting, the next logon request is assigned to the server with the lowest pending logons. If more than one server meets this criteria, the server with the lowest load index is selected.