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Storage area networks (SANs) can contain many disk drives that are dispersed across complex networks. This can make device discovery and device ownership difficult. iSCSI initiators must be able to identify storage resources in the SAN and determine whether they have access to them.
Internet Storage Name Service (iSNS) is a standards-based service that is available beginning with SUSE® Linux Enterprise Server (SLES) 10 Support Pack 2. iSNS facilitates the automated discovery, management, and configuration of iSCSI devices on a TCP/IP network. iSNS provides intelligent storage discovery and management services comparable to those found in Fibre Channel networks.
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iSNS should be used only in secure internal networks. |
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 discovery 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 discoveries and by limiting the amount of time each host spends establishing discovery relationships. This lets you control and simplify the number of targets and initiators that must be discovered.
Both iSCSI targets and iSCSI initiators use iSNS clients to initiate transactions with iSNS servers by 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.
Some of the benefits provided by iSNS for Linux include:
Provides an information facility for registration, discovery, and management of networked storage assets.
Integrates with the DNS infrastructure.
Consolidates registration, discovery, and management of iSCSI storage.
Simplifies storage management implementations.
Improves scalability compared to other discovery methods.
An example of the benefits iSNS provides can be better understood through the following scenario:
Suppose you have a company that has 100 iSCSI initiators and 100 iSCSI targets. Depending on your configuration, all iSCSI initiators could potentially try to discover and connect to any of the 100 iSCSI targets. This could create discovery and connection difficulties. By grouping initiators and targets into discovery domains, you can prevent iSCSI initiators in one department from discovering the iSCSI targets in another department. The result is that the iSCSI initiators in a specific department only discover those iSCSI targets that are part of the department’s discovery domain.
iSNS Server for Linux is included with SLES 10 SP2 and later, but is not
installed or configured by default. You must install the iSNS package
modules (isns
and yast2-isns
modules) and configure the iSNS service.
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iSNS can be installed on the same server where iSCSI target or iSCSI initiator software is installed. Installing both the iSCSI target software and iSCSI initiator software on the same server is not supported. |
To install iSNS for Linux:
Start YaST and select
.
When prompted to install the isns
package, click
.
Follow the install dialog instructions to provide the SUSE Linux Enterprise Server 11 installation disks.
When the installation is complete, the iSNS Service configuration dialog opens automatically to the
tab.![]() |
In
, specify the DNS name or IP address of the iSNS Server.In
, select one of the following:Specify the following firewall settings:
Open Port in Firewall: Select the check box to open the firewall and allow access to the service from remote computers. The firewall port is closed by default.
Firewall Details: If you open the firewall port, the port is open on all network interfaces by default. Click to select interfaces on which to open the port, select the network interfaces to use, then click .
Click
to apply the configuration settings and complete the installation.Continue with Section 12.3, “Configuring iSNS Discovery Domains”.
In order for iSCSI initiators and targets to use the iSNS service, they must belong to a discovery domain.
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The SNS service must be installed and running to configure iSNS discovery domains. For information, see Section 12.4, “Starting iSNS”. |
A default discovery domain named
is automatically created when you install the iSNS service. The existing iSCSI targets and initiators that have been configured to use iSNS are automatically added to the default discovery domain.To create a new discovery domain:
Start YaST and under
, select .Click the
tab.The
area lists all discovery domains. You can create new discovery domains, or delete existing ones.Deleting a domain removes the members from the domain, but it does not delete the iSCSI node members.The
area lists all iSCSI nodes assigned to a selected discovery domain. Selecting a different discovery domain refreshes the list with members from that discovery domain. You can add and delete iSCSI nodes from a selected discovery domain. Deleting an iSCSI node removes it from the domain, but it does not delete the iSCSI node.Creating an iSCSI node allows a node that is not yet registered to be added as a member of the discovery domain. When the iSCSI initiator or target registers this node, then it becomes part of this domain.
When an iSCSI initiator performs a discovery request, the iSNS service returns all iSCSI node targets that are members of the same discovery domain.
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Click the
button.You can also select an existing discovery domain and click the
button to remove that discovery domain.Specify the name of the discovery domain you are creating, then click
.Continue with Section 12.3.2, “Creating iSNS Discovery Domain Sets”.
Discovery domains must belong to a discovery domain set. You can create a discovery domain and add nodes to that discovery domain, but it is not active and the iSNS service does not function unless you add the discovery domain to a discovery domain set. A default discovery domain set named
is automatically created when you install iSNS and the default discovery domain is automatically added to that domain set.To create a discovery domain set:
Start YaST and under
, select .Click the
tab.The
area lists all of the discover domain sets. A discovery domain must be a member of a discovery domain set in order to be active.In an iSNS database, a discovery domain set contains discovery domains, which in turn contains iSCSI node members.
The
area lists all discovery domains that are assigned to a selected discovery domain set. Selecting a different discovery domain set refreshes the list with members from that discovery domain set. You can add and delete discovery domains from a selected discovery domain set. Removing a discovery domain removes it from the domain set, but it does not delete the discovery domain.Adding an discovery domain to a set allows a not yet registered iSNS discovery domain to be added as a member of the discovery domain set.
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Click the
button.You can also select an existing discovery domain set and click the
button to remove that discovery domain set.Specify the name of the discovery domain set you are creating, then click
.Continue with Section 12.3.3, “Adding iSCSI Nodes to a Discovery Domain”.
Start YaST and under
, select .Click the
tab.![]() |
Review the list of nodes to make sure that the iSCSI targets and initiators that you want to use the iSNS service are listed.
If an iSCSI target or initiator is not listed, you might need to restart the iSCSI service on the node. You can do this by running the rcopen-iscsi restart command to restart an initiator or the rciscsitarget restart command to restart a target.
You can select an iSCSI node and click the
button to remove that node from the iSNS database. This is useful if you are no longer using an iSCSI node or have renamed it.The iSCSI node is automatically added to the list (iSNS database) again when you restart the iSCSI service or reboot the server unless you remove or comment out the iSNS portion of the iSCSI configuration file.
Click the
tab, select the desired discovery domain, then click the button.Click
, select the node you want to add to the domain, then click .Repeat Step 5 for as many nodes as you want to add to the discovery domain, then click when you are finished adding nodes.
An iSCSI node can belong to more than one discovery domain.
Continue with Section 12.3.4, “Adding Discovery Domains to a Discovery Domain Set”.
Start YaST and under
, select .Click the
tab.Select
to add a new set to the list of discovery domain sets.Choose a discovery domain set to modify.
Click
, select the discovery domain you want to add to the discovery domain set, then click .Repeat the last step for as many discovery domains as you want to add to the discovery domain set, then click
.A discovery domain can belong to more than one discovery domain set.
iSNS must be started at the server where you install it. Enter one of
the following commands at a terminal console as the
root
user:
rcisns start
/etc/init.d/isns start
You can also use the stop, status, and restart options with iSNS.
iSNS can also be configured to start automatically each time the server is rebooted:
Start YaST and under
, select .With the
tab selected, specify the IP address of your iSNS server, then click .In the
section of the screen, select .You can also choose to start the iSNS server manually. You must then use the rcisns start command to start the service each time the server is restarted.
iSNS must be stopped at the server where it is running. Enter one of the
following commands at a terminal console as the
root
user:
rcisns stop
/etc/init.d/isns stop
For information, see the Linux iSNS for iSCSI project. The electronic mailing list for this project is Linux iSNS - Discussion.
General information about iSNS is available in RFC 4171: Internet Storage Name Service.