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Manual Chapter : Dynamic Ratio Load Balancing

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Dynamic Ratio Load Balancing

Introduction to dynamic ratio load balancing

You can configure Dynamic Ratio load balancing for pools that consist of RealNetworks® RealServer™ servers, Microsoft® Windows® servers equipped with Windows Management Instrumentation (WMI), or any server equipped with an SNMP agent such as the UC Davis SNMP agent or Windows 2000 Server SNMP agent.

To implement Dynamic Ratio load balancing for these types of servers, BIG-IP® Local Traffic Manager™ provides a special monitor plug-in file and a performance monitor for each type of server. The exception is a server equipped with an SNMP agent. In this case, the BIG-IP system provides the monitor only; no special plug-in file is required for a server running an SNMP agent.

Monitor plug-ins and corresponding monitor templates

For each server type, this table shows the required monitor plug-in and the corresponding performance monitor types.

Server Type Monitor plug-in Monitor Type
RealServer Windows server F5RealMon.dll Real Server
RealServer UNIX server f5realmon.so Real Server
Windows server with WMI f5isapi.dll or F5Isapi64.dll or F5.IsHandler.dll WMI
Windows 2000 Server server SNMP agent SNMP DCA and SNMP DCA Base
UNIX server UC Davis SNMP agent SNMP DCA and SNMP DCA Base

Overview of implementing a RealServer monitor

For RealSystem® Server systems, the BIG-IP® system provides a monitor plug-in that gathers the necessary metrics when you have installed the plug-in on the RealSystem Server system. Configuring a RealSystem Server for Dynamic Ratio load balancing consists of four tasks:

  • Installing the monitor plug-in on the RealSystem Server system
  • Configuring a Real Server monitor on the BIG-IP system
  • Associating the monitor with the server to gather the metrics
  • Creating or modifying the server pool to use Dynamic Ratio load balancing

Installing the monitor plug-in on a RealSystem server system (Windows version)

This task installs the monitor plug-in on a RealSystem Server system (Windows version).
  1. Download the monitor plug-in F5RealServerPlugin.dll from the BIG-IP system.
    The plug-in is located in the folder /usr/local/www/docs/agents.
  2. Copy F5RealServerPlugin.dll to the RealServer plug-ins directory. (For example, C:\Program Files\RealServer\plug-ins.)
  3. If the RealSystem Server process is running, restart it.
Once the plug-in is installed and compiled, you must configure a Real Server monitor, associate the configured monitor with the node (a RealSystem Server server), and set the load balancing method to Dynamic Ratio.

Installing and compiling a Linux or UNIX RealSystem server monitor plug-in

This task installs and compiles a Linux or UNIX RealSystem Server monitor plug-in.
  1. Using the .iso image, burn a CD-ROM of the BIG-IP system software.
  2. On the CD, navigate to the directory /downloads/rsplug-ins.
  3. Copy the file F5RealMon.src.tar.gz to the directory /var/tmp on the BIG-IP system.
  4. On the BIG-IP system, change to the directory /var/tmp: cd /var/tmp
  5. Use the UNIX tar command to uncompress the file F5RealMon.src.tar.gz:
    For example, you might enter tar -xvzf F5RealMon.src.tar.
  6. Change to the F5RealMon.src directory: cd F5RealMon.src
  7. Type the ls command to view the directory contents.
  8. To compile the source, use the instructions in the file build_unix_note.
  9. Start RealSystem Server.
Once the plug-in is installed and compiled, you must configure a Real Server monitor, associate the configured monitor with the node (a RealSystem Server server), and set the load balancing method to Dynamic Ratio.

Overview of implementing a WMI monitor

For Windows running Windows Management Instrumentation (WMI), the BIG-IP® system provides a Data Gathering Agent for the IIS server. Configuring a Windows platform for Dynamic Ratio load balancing consists of these tasks:

  • Installing the Data Gathering Agent on the IIS server
  • Configuring a WMI monitor on the BIG-IP system
  • Associating the monitor with the server to gather the metrics
  • Creating or modifying the server pool to use the Dynamic Ratio load balancing method
Important: To enable a user to access WMI metrics on a Windows server, you must configure the WMI monitor on the BIG-IP system correctly.

The procedure for installing the Data Gathering Agent on an IIS server differs depending on whether the server is running IIS version 5.0, 6.0, or 7.0, and whether the Data Gathering Agent is the file f5isapi.dll (or f5isapi64.dll), or the file F5.IsHandler.dll.

Tip: F5 Networks® recommends that you install only the Data Gathering Agent file that pertains to your specific configuration. Installing multiple Data Gathering Agent files could result in unwanted behavior.

IIS version support for the data gathering agent files

The procedure for installing the Data Gathering Agent on an IIS server differs depending on which IIS version the server is running and whether the Data Gathering Agent is the file f5isapi.dll, f5isapi64.dll, or F5.IsHandler.dll. This table shows each of the Data Gathering Agent files and the IIS versions that support each file.

Data Gathering Agent IIS 5.0 IIS 6.0 IIS 7.0 IIS 7.5 IIS 8.0 IIS 8.5
f5isapi.dll (32-bit) and f5isapi64.dll (64-bit) Yes Yes N/A N/A N/A N/A
F5.IsHandler.dll (32-bit, 64-bit, and .NET) N/A Yes Yes Yes Yes Yes

Installing the Data Gathering Agent F5.IsHandler.dll on an IIS 7.5 server

Important: Do not install the files f5isapi.dll or f5isapi64.dll on IIS version 7.5. For IIS servers running version 7.5, always install the file F5.IsHandler.dll.
This task installs the Data Gathering Agent F5.IsHandler.dll on an IIS 7.5 server.
  1. Create a scripts directory under the directory C:\Inetpub (C:\Inetpub\scripts).
  2. Create a \bin directory under the scripts directory (C:\Inetpub\scripts\bin).
  3. Copy the file F5.IsHandler.dll to the directory C:\Inetpub\scripts\bin.
  4. In the C:\Inetpub\scripts directory, create the file web.config. 
    <?xml version="1.0" encoding="UTF-8"?>
                    <configuration>
                        <system.webServer>
                            <handlers>
                                <clear />
                                <add name="F5IsHandler" path="f5isapi.dll" verb="*" type="F5.IsHandler"
                                    modules="ManagedPipelineHandler" scriptProcessor="" resourceType="Unspecified"
                                    requireAccess="Script" preCondition="" />
                            </handlers>
                            <security>
                                <authentication>
                                    <anonymousAuthentication enabled="false" />
                                </authentication>
                            </security>
                        </system.webServer>
                        </configuration>
    Important: In this example, the path value f5isapi.dll appears to be a mistake but is actually correct. It is the type value F5.IsHandler that directs the server to the correct file.
  5. Allow anonymous authentication to be overridden by using the appcmd command to set the override mode in the machine-level applicationHost.config file. 
    appcmd set config "Default Web Site/scripts"
/section:anonymousAuthentication
/overrideMode:Allow /commit:APPHOST
    Note: appcmd is located in \windows\system32\intesrv.
  6. Set up a new application pool for the file F5.IsHandler.dll:
    1. From the Start menu, choose Control Panel.
    2. Choose Administrative Tools.
    3. Choose Internet Information Services (IIS) Manager.
    4. From Connections, expand MachineName ( MachineName\UserName ).
    5. Right click the Application Pools menu and choose Add Application Pool.
    6. In the Name field, type F5 Application Pool.
    7. Click OK.
    8. From the Application Pools list, right click F5 Application Pool and choose Advanced Settings.
    9. Under the Process Model List, click Identity, and then click the button to the right of ApplicationPoolIdentity.
    10. From Built-in account select NetworkService.
    11. Click OK.
    12. Click OK.
  7. Create a new application named scripts:
    1. Expand Sites.
    2. Right click Default Web Site and choose Add Application.
    3. In the Alias field, type scripts.
    4. Change the application pool, click Select, select F5 Application Pool from the Application Pool list, and click OK.
    5. For the physical path, type the directory you created in step 1 (C:\Inetpub\scripts\).
    6. Click OK.
  8. Change the Authentication setting to Basic Authentication:
    1. Select scripts.
    2. In the center pane, double click Authentication.
    3. Verify that the status of all items under Authentication is Disabled, except for the Basic Authentication item. To enable or disable an authentication item, right click the name and choose Enable or Disable.
Once you have installed the plug-in, you must configure a WMI monitor, associate the configured monitor with the pool member, and set the load balancing method to Dynamic Ratio.

Installing the Data Gathering Agent F5.IsHandler.dll on an IIS 8.0 or 8.5 server

Important: Do not install the files f5isapi.dll or f5isapi64.dll on IIS version 8.0 or 8.5. For IIS servers running version 8.0 or 8.5, always install the file F5.IsHandler.dll.
This task installs the Data Gathering Agent F5.IsHandler.dll on an IIS 8.0 or 8.5 server.
  1. Create a scripts directory under the directory C:\Inetpub (C:\Inetpub\scripts).
  2. Create a \bin directory under the scripts directory (C:\Inetpub\scripts\bin).
  3. Copy the file F5.IsHandler.dll to the directory C:\Inetpub\scripts\bin.
  4. Allow anonymous authentication to be overridden by using the appcmd command to set the override mode in the machine-level applicationHost.config file. 
    appcmd set config "Default Web Site/scripts"/section:anonymousAuthentication/overrideMode:Allow /commit:APPHOST
    Note: appcmd is located in \windows\system32\inetsrv.
  5. Set up a new application pool for the file F5.IsHandler.dll:
    1. From the Start menu, choose Control Panel.
    2. Choose Administrative Tools.
    3. Choose Internet Information Services (IIS) Manager.
    4. From Connections, expand MachineName ( MachineName\UserName ).
    5. Right click the Application Pools menu and choose Add Application Pool.
    6. In the Name field, type F5 Application Pool.
    7. Click OK.
    8. From the Application Pools list, right click F5 Application Pool and choose Advanced Settings.
    9. Under the Process Model List, click Identity, and then click the button to the right of ApplicationPoolIdentity.
    10. From Built-in account select NetworkService.
    11. Click OK.
    12. Click OK.
  6. Create a new application named scripts:
    1. Expand Sites.
    2. Right click Default Web Site and choose Add Application.
    3. In the Alias field, type scripts.
    4. Change the application pool, click Select, select F5 Application Pool from the Application Pool list, and click OK.
    5. For the physical path, type the directory you created in step 1 (C:\Inetpub\scripts\).
    6. Click OK.
  7. Change the Authentication setting to Basic Authentication:
    1. Select scripts.
    2. In the center pane, double click Authentication.
    3. Verify that the status of all items under Authentication is Disabled, except for the Basic Authentication item. To enable or disable an authentication item, right click the name and choose Enable or Disable.
  8. Add a handler mapping:
    1. Select scripts.
    2. Click Handler Mappings.
    3. In the Actions pane on the right side of the screen, click Add Managed Handler.
    4. In the Request Path field, type F5Isapi.dll.
      Important: The Request Path value f5isapi.dll appears to be a mistake but is actually correct. It is the Type value F5.IsHandler that directs the server to the correct file.
    5. From the Type list, select F5.IsHandler.
    6. Type a name, such as F5 IsHandler.
    7. Click the Requested Restrictions button.
    8. Clear the check box labeled Invoke handler only if request is mapped to:
    9. Click OK.
    10. Click OK again.
Once you have installed the plug-in, you'll need to configure a WMI monitor, associate the configured monitor with the pool member, and set the load balancing method to Dynamic Ratio.
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