Wednesday, March 7, 2012

Global Server (Not Really) Load Balancing with Netscaler

Ran into an interesting scenario recently - Customer wants to serve Outlook Web Access from two data centers, but not the way you think  - I mean, not 'load balanced' - but as a DR mechanism only. All connections go to the primary data center, but must redirect to the DR data center if Primary is down, and fall back when Primary is back up.. read on..

With a normal GSLB configuration, you would create the load balancing services, the LB virtual servers, the GSLB site, the GSLB services, and GSLB servers with multiple services attached to each site (will put the details in another post some day..). Then you let the DNS and GSLB do the magic, redirecting the resources to the available sites based on configured policies..

However, in the above scenario, the only thing that's different would be that instead of configuring multiple services, you would specify a backup GSLB virtual server. Simple! ..but hidden behind one of the tabs on the configuration page, not sure a lot of people notice that.

Here is a couple of screen shots from my lab. The first screen shows the GSLB server configuration with the load balancing virtual server for primary site (gslb_svc_web_site1) selected.

GSLB server configuration showing the primary LB virtual server selected.

Now, you select the 'Advanced' tab, and notice that there is an option for a 'Backup Vserver'. As long as you have configured a second GSLB virtual server for the remote site, it will display in the drop box and can be selected (shown gslb_svr_web_site2).

Backup VServer configuration in the Advanced tab

And there you go.. Global Server "not really" Load Balancing between two sites :-).


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