Intergraph WebScale User Manual page 72

WebScale™
to make sure that the dedicated IP address is first in the list. You can also use
multiple NIC's to avoid this problem.
Problem: Cluster does not load balance.
Description: WebScale is not load balancing my application(s), and the default host
handles all network traffic.
Probable cause(s) and resolution:
1. A port rule is missing. By default, WebScale directs all incoming network traffic
for the cluster IP address(es) to the default host. This ensures that application
you do not want load balanced will behave properly. To load balance an
application across the cluster, you should create a port rule on every cluster host
for the TCP/IP port(s) serviced by the application.
Problem: Load-balanced application does not work properly.
Description: The application that I am load balancing does not appear to work correctly
when running WebScale.
Probable cause(s) and resolution:
1. All of the application's ports are not being load balanced. Some applications
require multiple ports to perform their functions. For example, FTP uses ports 20
and 21. If both ports are not load balanced (usually with one port rule), the
application will not work correctly. Check that the applicable port rule covers all
ports used by the application and be sure to enable client affinity (single or Class
C).
2. The application is not started on all cluster hosts. WebScale does not start or
control applications. You should check that the application has been started on
every cluster host. If an application fails, you can disable its associated port
range using the webscale disable command.
3. The application should not be load balanced. Applications that update a file on
the local cluster host may not work correctly when load balanced because
multiple instances of the application may conflict when attempting to update a
common file. For example, email, groupware, and database servers often have
this problem. Do not load balance an application until its data sharing
requirements are thoroughly understood and met.
4. The application is not a TCP/IP service. WebScale load balances applications by
distributing incoming client requests among the cluster hosts. If a server
application is not structured as a TCP/IP service that receives client requests, it
will not benefit from using WebScale, and you will not observe load balancing.
5. Your firewall is proxying client traffic and making it appear as if all connections
are originating from the same client IP address. If a load balancing rule is
configured with Single affinity then all traffic will be handled by the same cluster
host. Turn off address translation (proxying) on the firewall or change affinity
from Single to None. Note that you may need Single affinity in order to provide
session support.
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User's Guide