Multiple Forefront UAG servers can be combined into an array.

Provides:

  • Scalability - grouping multiple servers in an array increases capacity for throughput and number of users
  • Fault tolerance - multiple servers provide the same services for endpoint devices
  • Failover - If an array is load balanced, endpoint devices request trunks via a VIP, and the request is handled by any array member (if an array member fails end, users might need to reauthenticate when transfered to another array member). In a non-load balanced array, each array member has a separate IP address (a.k.a. DIP). Transparent failover will require a method for updating name resolution, so that portal names resolve to the IP address of the correct array member.

Characteristics:

  • Each server in an array has the same configuration, including trunks, published applications, custom files, and VPN settings. Some server-specific settings are maintained, including passwords and certificates.
  • You can load balance array traffic using Windows Network Load Balancing (NLB) integrated into UAG, or using a hardware load balancer.
  • No separate server is required for array management. One of the array servers is designated as the array manager.
  • The configuration is stored in an Active Directory Lightweight Directory Services (AD LDS) instance, running on the array manager.
  • UAG settings can only be configured on the array member that is designated as the array manager. On other array members you can only run the Array Management Wizard to manage array settings.
  • An array with NLB enabled supports up to 8 array members

Deployment:

To deploy an array you need to:

  • Configure an array manager
  • Join servers to the array
  • Configure load balancing for the array using either an external load balancer or the Windows Server 2008 NLB feature.

Operations:

Managing an array consists of:

  1. Adding and removing array members
  2. Designating a different array member to act as the array manager
  3. Changing the credentials used by the array manager or array members

Troubleshooting:
If you join an UAG server to an array, and do not finish the Getting Started Wizard properly as instructed you may run into issues. For example you can see the following error message:The UAG configuration cannot be retrieved from Forefront TMG storage.

An error has occured and UAG will close. Check that TMG services are running. If the UAG server is a domain member, verify connectivity to the domain controller.

To resolve this, open UAG Management on the new member you are trying to join and finish the Getting Started Wizard as instructed. Note that you will receive explicit instructions by the wizard.

More info