IPV6 High Availability Web server cluster on IBM i HTTP server

Today, more and more enterprises recognize the importance of high availability (HA) for their WEB servers, after all, customers need reliable services. At the same time, more and more organizations are beginning to transition from IPV4 standard to http://www.aliyun.com/zixun/aggregation/9485.html ">ipv6 standard. The new requirements for supporting high-availability WEB services in IPV6 environments arise.

The high availability of WEB servers within the IPV6 environment can be achieved using the IBM PowerHA systemmirror for I software. This article describes an easy way to extend the IPV4 high available HTTP server cluster on IBM i to the IPV6 environment.

IBM PowerHA Systemmirror for I

The highly available HTTP servers in the IBM I operating system support three types of Web server cluster models:

uses the primary or backup model that takes over IP: The WEB server runs on the master node and on all backup nodes. Backup nodes are idle, and if the primary Web server fails or requires failover, these backup nodes can be converted to the primary Web server at any time. All client requests are always handled by the master node. The main model or backup model of the network dispatcher: similar to the main model or backup model that takes over IP, the WEB server runs on both the master node and all backup nodes. The backup node is idle and all client requests are processed by the master node. The network dispatcher, such as IBM Websphere®edge server, sends client requests to the WEB server. Peer-to-peer model: There are no explicitly declared master nodes in this model. All nodes are active and can handle client requests. Network dispatchers, such as IBM WebSphere Edge Server, distribute requests evenly across cluster nodes. This ensures that resources are distributed when the load is heavier. However, if there are too many nodes, linear scalability will not be guaranteed. With a certain number of nodes added, scalability can even disappear, and cluster performance is severely degraded.

This article describes how to extend high availability to the IPV6 high-availability WEB server cluster on the first model, IBM I HTTP server. The other two models require an additional network dispatcher, such as IBM WebSphere Edge Server, which is no longer described in this article.

The following figure shows the main model or backup model that takes over IP in the IPV6 network.

Figure 1. Figure 1. Main model or backup model taking over IP--Solution definition

If the primary node fails or the administrator deactivates the master node, the failover process is initiated. The following steps are performed in the failover:

1. A backup server is transferred to the primary node (in the order of switching, the node should be the first backup node).

2. Client requests are redirected to the new master node. If this client is not running a persistent Common Gateway Interface (CGI) application, failover will be completely transparent.

3. If the new master receives a user request belonging to a long-running session that is updated with a CGI program that is highly available, the server stores the request status. The new master node retrieves the state information of the highly available CGI program from the clustered hash list. Clustered hash lists are part of the state replication mechanism.

4. After the failed node is restored, you can restart the highly available Web server instance, which then becomes the backup system. If your system administrator wants the failed node to become the primary node again, you must perform a manual switch.

Software Requirements

For a master model or backup model that takes over IP in IPv6, the following licensing procedures and program temporary patches (PTF) must be available.

Licensing procedures:

5770ss1 HA can switch resources

5770DG1 *base IBM HTTP Server for I

5770HAS *base IBM PowerHA systemmirror for i Standard Edition

5770HAS 1 IBM PowerHA systemmirror for i Enterprise Edition

Required PTF:

-Latest PTF Group for 5770DG1 (min. sf99368-level 10)

Although IBM I supports IPv6 from 5th edition 2nd release (V5R2), IPV6 HA cluster support requires an IBM I 7.1 release.