10

Working with Global Availability Load Balancing

• Overview of the Global Availability load balancing mode
• Configuring the Global Availability mode

Overview of the Global Availability load balancing mode

You can use the Global Availability mode in one of two ways: either to load balance among wide IP pools, or to load balance within a wide IP pool. When you use the Global Availability mode to load balance among pools, the 3-DNS continually sends requests to the first pool in the wide IP. When all the virtual servers in the pool become unavailable, the pool is marked unavailable and the 3-DNS starts sending requests to the next pool listed in the wide IP. When the first pool is available again, the 3-DNS stops sending requests to the second pool, and starts sending them to the first pool again. If you have an origin site and an overflow network, such as a CDN, you can use Global Availability to load balance between the two networks.

When you use the Global Availability mode to load balance virtual servers within a pool, the load balancing works in much the same way. The 3-DNS repeatedly selects the first available virtual server in the wide IP pool to respond to requests. If that virtual server becomes unavailable, subsequent connections go to the next available virtual server listed in the pool. When the first listed virtual server becomes available again, the 3-DNS distributes requests to it again.

Figure 10.1 shows the 3-DNS using the Global Availability load balancing mode.

Figure 10.1 Global Availability mode

Configuring the Global Availability mode

The following sections describe how to configure the Global Availability load balancing mode to load balance among pools and to load balance within a pool.

To configure the Global Availability load balancing mode among pools using the Configuration utility

1. In the navigation pane, click Wide IPs.
2. In the Wide IP column, click a wide IP name.
   The Modify Wide IP screen opens.
3. In the Pool LB Mode box, select Global Availability.
4. Click Update.
5. A popup screen appears, indicating that with the Global Availability load balancing mode you must order the pools. Click OK.
   The Modify Virtual Servers screen opens.
6. In the Order column, specify the order in which you want to list the pools for Global Availability.
7. Click Update.

To configure the Global Availability load balancing mode among pools from the command line

1. At the command prompt, type 3dnsmaint to open the 3-DNS Maintenance menu.
2. On the 3-DNS Maintenance menu, select Edit 3-DNS Configuration to open the wideip.conf file.
3. Locate the wideip statement you want to edit.
4. Define Global Availability as the pool_lbmode.
5. List the pools in the wide IP in descending order of preference.

To configure the Global Availability load balancing mode within a pool using the Configuration utility

1. In the navigation pane, click Wide IPs.
2. In the Wide IP column, click a wide IP name.
   The Modify Wide IP screen opens.
3. On the toolbar, click Modify Pool.
   The Modify Wide IP Pools screen opens.
4. In the Pool Name column, click the name of a pool.
   The Modify Load Balancing screen opens.
5. Select Global Availability as the Preferred, Alternate, or Fallback load balancing mode.
6. Click Update.
7. A popup screen appears, indicating that with the Global Availability load balancing mode you must order the virtual servers. Click OK.
   The Modify Virtual Servers screen opens.
8. In the Order column, specify the order in which you want to list the virtual servers for Global Availability.
9. Click Update.

To configure the Global Availability load balancing mode within a pool from the command line

1. At the command prompt, type 3dnsmaint to open the 3-DNS Maintenance menu.
2. On the 3-DNS Maintenance menu, select Edit 3-DNS Configuration to open the wideip.conf file.
3. Locate the wideip statement you want to edit.
4. Define Global Availability as the preferred, alternate, or fallback load balancing mode within the pool that you want to modify.
5. List the virtual servers in the wide IP in descending order of preference. See Figure 10.2 on page 10-4 for an example of the syntax.

A Global Availability configuration example

With the Global Availability load balancing mode, you can configure one data center as your primary service provider and have several alternate service providers on standby. In the wideip statement, list the virtual servers in descending order of preference. The first available virtual server is chosen for each resolution request.

Figure 10.2 shows a sample wideip definition, in the wideip.conf file, where Global Availability is the preferred load balancing mode.

Figure 10.2 Configuring a standby data center using Global Availability

 // Global availability    
   wideip {    
      address           192.168.101.50    
      port              80 // http    
      name              "cgi.wip.domain.com"    
      pool {    
         name           "mypool"    
         preferred      ga    
         address       192.168.101.60 //New York data center    
         address       192.168.102.60 //Los Angeles data center    
         address       192.168.103.60 //Tokyo data center    
      }    
   }    

The first listed virtual server (192.168.101.60 in this example) receives all resolution requests unless it becomes unavailable. If the first listed virtual server does become unavailable, then the 3-DNS sends resolution requests to the second listed virtual server until the first listed virtual server becomes available again.