Crash Course on New Standards for IP Network Storage Compatibility

The success of IP storage will depend heavily on the vendor community adopting compatible standards into SAN devices and switches. For example, iSCSI has become the driving technology for creating IP-based SANS. iSCSI, along with the progress made by other standards, should help IP reach broad acceptance among vendors, customers, and systems integrators. Below is an overview of what each of these new standards has to offer:

iSCSI This emerging standard enables block-level storage data to be accessed anywhere within a TCP/IP network, including the Internet. iSCSI does this by transmitting native SCSI over a layer of the IP stack, encapsulating SCSI data and representing it as a series of bytes preceded by iSCSI headers. All hosts and SAN devices, such as storage arrays and tape, switches, routers and gateways, and host-bus adapters can use the iSCSI standard to lessen overhead on the host. iSCSI has emerged as the best way to transmit storage over IP networks. In fact, this standard should appeal to server and networking specialists who dont want to learn Fibre Channel.

FCIP A proposed standard, Fibre Channel over IP (FCIP) aims to connect islands of Fibre Channel SANs over IP networks, greatly extending existing Fibre Channels reach. FCIP works by first encapsulating Fibre Channel frames, which already contain the SCSI protocol, over TCP/IP links, and then unwrapping the Fibre Channel frames at the receiving end. FCIP solutions already exist. However, IT departments that use FCIP may find themselves locked into Fibre Channel for their servers, subsystems, and SAN switches.

iFCP More centered around TCP/IP than FCIP, the Internet Fibre Channel Protocol (iFCP) provides a lightweight gateway-to-gateway protocol for linking Fibre Channel devices into an existing IP infrastructure. iFCP uses TCP/IP for controlling congestion, error detection and error recovery. iFCP can be used to replace FC switches with an IP-based Ethernet fabric.

iSNS A standard proposed by Nishan Systems and supported by IBM and Intel, iSNS, which stands for Internet Storage Naming Service, provides discovery and naming services for IP-based SAN storage devices and resources. iSNS could emerge as an important part of the iSCSI puzzle, since it resolves compatibility issues among iSCSI devices, and also offers compatibility with FC naming conventions.

Gigabit Ethernet IP-oriented storage can run easily on native Gigabit Ethernet. With a nominal speed of 1.25 gigabits per second and 10 gigabits per second coming soon, Gigabit Ethernet has become ubiquitous in both business and carrier networks. Network service providers already offer low-cost, high-speed optical Gigabit Ethernet links. Even 100-megabits per second Fast Ethernet can deliver storage throughput of 2 megabits per second in company LANs. This speed is fast enough for certain SAN applications.

New standards, however, mean little until they are adopted and get built into products that are compatible with each other.