If there is trust between the AD domains, then you only need to join one. No need to use Access Zones in that case.  However, Access Zone can be used here if you have share name overlap. Example: there is "home" share on both servers and you want to be able to redirect the users by changing DNS, but not have to reconfigure the clients or login scripts run on the clients. In the long run, in most cases, it's best to change the client configs and use different share names. It keeps things simpler.  Access Zones are used in share name overlap case, but it's most commonly used with you multiple AD domains with no trust relationships. Often in an acquisition scenario where trust have not been created.
Hello,  I am looking to implement an Isilon cluster. Currently there are 3 clustered windows file servers and I am migrating to Isilon. The clusters are on two subnets a 10. and 172. and two AD domains the domains are trusted. I am wondering if I need to create access zones and divide up the cluster that way or if I can just list the multiple AD servers since they are trusted...  Any help is greatly appreciated
Isilon in multiple subnet/Multiple AD domains