An Internet Storage Name Service (iSNS) Server processes iSNS registrations and queries from iSNS clients. It maintains a database to manage the registrations.

The role of the iSNS Server in an iSCSI SAN is to allow iSCSI initiators and iSCSI targets to register and to query for other registered iSCSI initiators or iSCSI targets.

A Discovery Domain (DD) is a security and management mechanism that iSNS Servers use to administer access and connectivity to iSCSI initiators or iSCSI targets (storage nodes) in an iSCSI SAN.

A Discovery Domain Set (DDS) is a mechanism to store sets of discovery domain mappings in an iSNS database. A discovery domain set may contain one or more discovery domains and a discovery domain can be a member of one or more discovery domain sets. Multiple discovery domain sets may be active at the same time.

For the purpose of query and registration, discovery domains are viewed as containers for storage nodes and portal objects. A discovery domain is active if it is a member of at least one active discovery domain set. Discovery domains that are not members of an enabled discovery domain set are considered disabled. A storage node can be a member of one or more discovery domains. An enabled discovery domain establishes connectivity among the storage nodes in that discovery domain.

At the storage node level, a discovery domain is used to make iSCSI targets inaccessible to the iSCSI initiators that are not members of the discovery domain. When first identified by the iSNS server, the Default DD in an iSCSI SAN contains all storage nodes except ones already assigned to a discovery domain.

SFW enables you to register with Microsoft's iSNS service and to manage discovery domains and discovery domain sets.