The standby GSSM is a Cisco Global Site Selector 4480 running Cisco GSS software and performing GSLB functions for the GSS network. In addition, the standby GSSM is configured to act as the GSSM should the primary GSSM suddenly go off line or become unavailable to communicate with other GSS devices.
As with the primary GSSM, the standby GSSM is configured to run the GSSM GUI and contains a duplicate copy of the embedded PostgreSQL GSS database that is currently installed on the primary GSSM. Any configuration or network changes affecting the GSS network are synchronized between the primary and the standby GSSM so that the two devices are never out of step.
For more information : http://www.cisco.com/en/US/products/hw/contnetw/ps4162/products_configuration_guide_chapter09186a00800ca80e.html#1087000