the "backup/DR" interface is for configurations with replicated NAS servers  on replicated NAS servers the production interfaces are active on the src NAS server and the backup interfaces are active on the (readonly) dst NAS server use case is if you want to access the dst without a failover - for example for backup or testing or file restore
Unity > File > NAS Server > Properties > Network  NAS Server protocol - SMB only  When I click on + to add an interface, there are two choices. 1) Production IP Interface 2) IP Interface for Backup and Test. Questions: What is the "IP Interface for Backup and Test" valid for a NAS server environment for SMB only? Is "IP interface for backup and test" valid for current release or is this a future release feature for SMB only environments?
Unity NAS Server Network Interfaces