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Novell exteNd App Server Cluster Implementation on NetWare 6.5

Novell Cool Solutions: Feature
By James Lee

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Posted: 4 May 2004
 

Some people seem confused about Novell exteNd App Server cluster implementation on NetWare 6.5. Novell engineer James Lee gives you the run down.

There are two types of clustering that can be implemented with exteNd App Server on NetWare 6.5. One is application-level clustering and the other one is hardware-level clustering a.k.a. Novell Cluster Services. Although they serve the same main purpose of providing fault tolerance, application-level clustering has more to offer. Here's a quick comparison on their features and requirements:

Application-level Hardware-level
Hardware-level Failover YES YES
Session-level Failover NO NO
Load Balancing YES NO
Cache Management YES NO
Additional Hardware NO YES

Application-level clustering is one of the built-in features of the Novell exteNd App Server and therefore requires no additional hardware. Application-level clustering also allows you to manage or distribute load between participating servers by assigning "weight" to each server, which you can't do with hardware-level clustering. One thing that is not supported in either configuration is Session-level failover - ability to seamlessly migrate user data/state when failover occurs. You will need a special device like an L4 switch or third-party load balancing solution to handle session-level failovers.

Creating application-level cluster (in simple steps)

  1. Install exteNd App Server on two or more servers.


  2. During the install, you may point to the database that will be shared across all servers

    OR

    After the install, edit the following line in SYS:\EXTEND\APPSERVER\RESOURCES\HTTPD.PROPS on all servers to point to the same SilverMaster50 database:

    http-server.Jdbc.URL=jdbc:mysql://<server that hosts the MySQL database>/SilverMaster50

    The database is created by executing SilverMasterInit(.nlm) either during the install or after the install.

    The server that hosts the MySQL database can be one of the participating servers or a separate server dedicated for MySQL database.


  3. Load SilverCacheMgr, SilverDispatcher, SilverLoadMgr and SilverServer (always in that order!) on the server that will act as the "distributer."


  4. Load SilverServer on all other servers.


  5. Using SMC, create a new cluster. Add servers to your cluster and accept default ports for all settings.


  6. Restart SilverCacheMgr, SilverDispatcher, SilverLoadMgr and SilverServer in the same order.


  7. Your cluster is up and running at http://<your_ip>:54892 if you see the following message when you load SilverServer:

    ==> registering <your_ip>:83 with load balancer manager <your_ip>:54891

NOTE: If you used ip addresses when creating your cluster, you must load SilverServer with "-host <ip_address>" flag. This bug will be fixed in the later release of exteNd App Server.

Creating hardware-level cluster

The main idea behind creating a hardware-level cluster is that you host MySQL database on a shared volume and load/unload MySQL (mysqld_safe.nlm) and exteNd App Server (silverserver.nlm) every time a node goes down or fail over occurs. For more information, please refer to this section of the documentation.

If you have any questions you may contact James at jalee@novell.com


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