Product Documentation

Manage Server OS machine server load

May 10, 2015

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 (Default)
  • 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. (Needs to be set by Citrix policies)
  • Concurrent logon tolerance setting, which is the allowed number of concurrent requests to log on to the server. (Default)

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 XenApp and 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.

Change server load management policy settings

Server OS machine policies determine which settings calculate server load.

Note: This release does not support the XenApp Load Evaluator setting created for XenApp 6.5.

The default Load Management settings work for most Server OS machine environments. However, if you want to change these settings, policies are available to adjust loading. See Load Management policy settings.

Servers delivering Server OS machines have default load management settings to make sure that sessions are balanced between servers. Use the Load Management policy to change the following settings.

Note: A value of -1 for any of the following settings indicates this setting is excluded from load calculation.
Policy setting Load management factor Description Value

Concurrent logons tolerance

The number of concurrent logons a server can accept

Enabled (default): Sets the maximum number of concurrent logons

Disabled: Excludes this setting from load calculation

Positive integer

(default 2)

CPU usage

CPU usage percentage

Enabled: Defines the CPU use percentage at which the server reports a full load

Disabled (default): Excludes CPU usage from load calculation

1 through 100 percent

(default 90)

CPU usage excluded process priority

Priorities at which the CPU usage for a process is excluded from the CPU Usage load index

Enabled (default): excludes processes from CPU Usage load index based on the selected value

Disabled: Ignores the configuration of this setting

Below Normal or Low — Excludes processes that have a priority or Below Normal or Low

Low — Excludes processes that have a priority or Low

(default: Below Normal or Low)

Disk usage

Disk queue length

Enabled: Defines the Disk queue length at which a server reports 75% full load

Disabled (default): Excludes Disk usage from the load calculation

Integer value

(default 8)

Memory usage

Memory usage percentage

Enabled: Includes memory use data in load calculations

Disabled (default): Excludes memory use data in load calculations

1 through 100 percent

(default 90)

Memory usage base load

Memory usage in MBs

Defines the memory use in MBs up to the point at which the server reports no load due to memory usage. It is common for basic operating systems functions to consume several hundred MBs of memory.

Enabled (default): Excludes an approximation of the base operating system memory usage from the server's load index

Disabled: Does not exclude base load value from the memory usage

1 through Installed memory in MBs

(default 768)

Maximum number of sessions

Maximum number of sessions on a server

Enabled (default): Sets the maximum number of sessions on the server

Disabled: Excludes this setting from load calculation

1 through Maximum integer

(default 250)

To change load management policy settings

  1. In Studio, access the New Policy Wizard by selecting the Policy node.
  2. Select the Categories node and then select Load Management. The load management settings described in the previous table appear.
  3. Click Add to display the Edit Settings window.
  4. By default, the setting is enabled. You can change the setting value.
  5. To return the setting to its default, click Use default value.