Peaceful Coexistence Of Fibre Channel And IP Storage - Technology Information

Computer Technology Review, July, 2001 by Brent Ross

Fibre Channel and IP Storage SANs will coexist because they have different strengths and are suited for different applications and markets. Fibre Channel will continue to be a good SAN solution in enterprise data centers. IP Storage, with a lower projected total cost of ownership (TCO), will become widely adopted in small and midsized companies and data centers. IP storage protocols now being standardized will also be used to connect Fibre Channel SANs to each other.

Fibre Channel

Fibre Channel's strengths (Figure 1) include high performance with relatively low latency, and the ability to connect across campus distances. Also, Fibre Channel products are generally available today from a wide range of storage and interconnect vendors. Users who have already made an investment in Fibre Channel technology and skills have already paid much of the "cost of entry." For those who haven't, customers have the benefit of lessons learned by the earlier adopters.

Fibre Channel was developed specifically to attach servers to storage as efficiently as possible in a variety of topologies. Fibre Channel specifications address the need for scalability, availability, and distance. FC-AL (Fibre Channel-Arbitrated Loop) configurations incorporate redundancy and switched FC fabric provides redundancy, alternate path routing, and zoning.

With 1 Gbps Fibre Channel products currently available, peak full-duplex throughput of 200MB/sec is achievable. With the new 2Gb products now appearing, it's possible to double that throughput. Focus is also beginning to shift to 10Gbps.

Support for Fibre Channel has been built into most storage management applications, and a new class of applications--SAN management--has emerged.

Typically, for end-user adoption of any new technology, a wide variety of vendors must bring products to market to provide function, feature, and price competitiveness, allowing users choices and the opportunity to switch vendors. Fibre Channel has achieved the necessary critical mass of alternative products and technology sources.

Given the strengths of Fibre Channel, it is an appropriate choice for large enterpriselevel companies for applications that require the highest performance, and whose budget allows for a dedicated infrastructure and skills.

Because of the distance limitations inherent in a Fibre Channel SAN, suitable applications are those where storage subsystems are grouped within a data center or nearby at campus-type distances.

Fibre Channel SANs will continue to be deployed in large enterprise-level data centers for the next few years, but widespread deployment outside of these large installations is unlikely to occur.

Complete end-to-end Fibre Channel solutions such as LAN-free backup are starting to emerge in the distribution channels. This will provide an opportunity for Fibre Channel to move into markets that do not yet have any Fibre Channel products. These customers will need to assess the extent and timing of their need for SAN technology, and whether or not to wait for IP Storage SAN solutions.

IP storage

IP Storage (Figure 2) can be used either to implement SANs or to connect geographically dispersed SANs together thereby enhancing and extending the life of FC SANs. IP Storage can be viewed as an additional market enabler of Fibre Channel SANs. However, the greatest potential for IP Storage is as an alternative to Fibre Channel to implement SANs using the iSCSI protocol now being standardized.

iSCSI is the Internet Engineering Task Force (IETF) specification that defines how SCSI and Ethernet work together to perform SCSI data transfers across TCP/IP networks. It allows today's block storage SCSI commands to be carried by the standard TCP/IP protocols over Ethernet. The SCSI and Ethernet standards are each mature, stable, ubiquitous, and interoperable. These qualities provide a solid foundation on which to build a SAN fabric.

For the next two or three years, until broad deployment of 10Gb Ethernet, Fibre Channel will continue to offer higher peak performance and lower latency than IP Storage. However, many applications that work well with 1Gb Fibre Channel today will work equally well on 1Gb Ethernet.

With the increasing popularity of 1Gbit Ethernet, building iSCSI SANs will become increasingly attractive to small and mid-sized organizations where the high cost and complexity of Fibre Channel is not an option. iSCSI maintains all of the manageability, cost effectiveness, versatility, and compatibility that has made Ethernet the dominant networking technology today. Also, Network Attached Storage (NAS) products and filers are becoming increasingly common, so the notion of attaching storage boxes to Ethernet networks has already been embraced by customers of all sizes.

A vast array of Ethernet equipment and tools are available from many vendors today, and they are fully interoperable. 1Gbps Ethernet equipment supports the installed base of earlier (10Mbps, 100Mbps) Ethernet equipment. A user buying Ethernet infrastructure products can be confident they will be compatible and interoperable with equipment from other suppliers. The same cannot be said for Fibre Channel products, however.