Internet Storage Name Service brings the plug-and-play capabilities of Fibre Channel to IP storage networks. ISNS facilitates automated discovery, management and configuration of iSCSI and Fibre Channel devices on a TCP/IP network. In a Fibre Channel fabric, a simple name server provides these services.
In any storage network, servers (or initiators) need to know which storage resources (or targets) they can access. One way to accomplish this is for an administrator to configure each initiator manually with its own list of authorized targets and configure each target with a list of authorized initiators and access controls. But this process is time-consuming and error-prone, and accidentally configuring multiple servers to access the same storage resources could be disastrous.
An Internet storage name server lets servers automatically identify and connect to authorized storage resources. Letting the servers dynamically adapt to changing storage resource membership and availability without human intervention results in even more efficiency.
Whereas a Fibre Channel storage name server can handle only Fibre Channel devices, iSNS can accommodate iSCSI devices and Fibre Channel devices via the Internet Fibre Channel Protocol. End nodes (initiators and targets) in an iSNS environment run a lightweight iSNS client that represents the host device to the iSNS server.
ISNS provides the following services:
* Name registration and discovery services – Targets and initiators register their attributes and address, and then can obtain information about accessible storage devices dynamically.
* Discovery domains and logon control service – Resources in a typical storage network are divided into groupings called discovery domains, which can be administered through network management applications. Discovery domains enhance security by providing access control to targets that are not enabled with their own access controls, while limiting the logon process of each initiator to a relevant subset of the available targets in the network.
* State-change notification service – The iSNS server notifies relevant iSNS clients of network events that could affect the operational state of storage nodes. Events such as storage resources going offline, discovery domain membership changes and link failure in a network can trigger state-change notifications. These notifications let a network quickly adapt to changes in topology, which is key to scalability and availability.
* Open mapping of Fibre Channel and iSCSI devices – The iSNS database can store information about Fibre Channel and iSCSI devices and mappings between the two in a multi-protocol environment. The mapped information is then available to any authorized iSNS client. This centralized approach is open and scalable instead of retrieving the mappings from individual iSCSI-FC gateways using proprietary mechanisms.
ISNS clients discover the iSNS server or servers using a variety of mechanisms, including Dynamic Host Configuration Protocol, Service Location Protocol and broadcast or multicast heartbeat messages. The iSNS framework allows for back-up iSNS servers that provide redundancy and failover.
ISNS servers also can store and distribute X.509 public-key certificates used for authenticating iSCSI storage nodes during the logon process.
By facilitating a seamless integration of IP and Fibre Channel networks, iSNS provides value to any storage network composed of iSCSI and/or Fibre Channel devices. The iSNS specification is on the standards track with the Internet Engineering Task Force IP Storage Working Group and is expected to be classified as a proposed standard soon.
Pammidimukkala is a director of product management for Nishan Systems Inc. and is the iFCP subgroup chair in the SNIA IP Storage Forum. He can be reached at prasad@nishansystems.com.
