1.1 How iSNS Works

For an iSCSI initiator to discover iSCSI targets, it needs to identify which devices in the network are storage resources and what IP addresses it needs to access them. A query to an iSNS server returns a list of iSCSI targets and the IP addresses that the initiator has permission to access.

Using iSNS, you create iSNS discovery domains and discovery domain sets. You then group or organize iSCSI targets and initiators into discovery domains and group the discovery domains into discovery domain sets. By dividing storage nodes into domains, you can limit the login process of each host to the most appropriate subset of targets registered with iSNS, which allows the storage network to scale by reducing the number of unnecessary logins and by limiting the amount of time each host spends establishing login relationships. This lets you control and simplify the number of targets and initiators that have access to each other.

Figure 1-1 iSNS Discovery Domains and Discovery Domain Sets

iSNS clients initiate transactions with iSNS servers using the iSNS protocol. They then register device attribute information in a common discovery domain, download information about other registered clients, and receive asynchronous notification of events that occur in their discovery domain.

iSNS servers respond to iSNS protocol queries and requests made by iSNS clients using the iSNS protocol. iSNS servers initiate iSNS protocol state change notifications and store properly authenticated information submitted by a registration request in an iSNS database.