SAN alternatives

There's more than one way to build a storage-area network. Vendors continue to announce standards and plans for alternative storage network technologies.

Our research indicates that SANs are currently comprised of predominantly four technologies: Fibre Channel Arbitrated Loop (FC-AL), switched Fiber Channel (FC-S), Gigabit Ethernet and SCSI. It is safe to say at this point there is not one dominant technology. And many SANs utilize more than one of these connection technologies, further compounding the issue of determining which is best for you.

Interestingly, when we question IT professionals about their reasons for choosing their preferred storage network technology, the reasons are often similar, regardless of the technology chosen. It would appear that distinguishing among these alternatives is not an easy matter, or perhaps it is a very individual decision for each implementation.

Wide availability of staff skilled in a particular technology is often mentioned as a reason for implementing all the technologies, including the newer FC-AL and FC-S.

Speed is another reason frequently mentioned. Again, speed is a reason cited for every technology, indicating there is currently no leader. Partially, this is due to leapfrogging announcements and performance enhancements in each of the technologies, so the race for first place changes with each day. Also, much like professional sports, it comes down to "any given Sunday" - that is, the fastest technology may be more dependent upon the individual implementations than on any inherent speed advantages of the technologies.

Interestingly, cost is mentioned most often as a motivator for selecting SCSI. Given the pervasiveness of SCSI adapters and the relatively low cost to implement SCSI connections, this is easy to understand. With the plans of the SCSI Trade Association to increase the speed of SCSI while maintaining backwards compatibility, SCSI may continue to be thought of as having a distinct cost advantage over other SAN technologies.

It will be interesting to watch Gigabit Ethernet as a storage networking technology, as the price of adapters and network devices fall to the point where 100M bit/sec Ethernet is today. Adaptec, a well-known maker of SCSI adapters, recently announced its EtherStorage technology to provide high-performance storage services over Gigabit Ethernet using specialized adapters. Given Adaptec's proven expertise in SCSI adapters, this may serve as another boost to the rise of Gigabit Ethernet as a storage network.

Where does this leave Fibre Channel? It continues to be used in many SANs, and prices continue to fall as volumes and competition increase. New software products are announced constantly to add services and manageability to Fibre Channel SANs. So Fibre Channel is still definitely in the race and should be considered as an alternative by anyone planning a SAN.

How do you decide which technology or technologies are right for your organization? First, look carefully at your environment, evaluating the technical requirements as well as your organization and resources. Also, determine what the motivations for your SAN implementation are and stick to them as the decision criteria throughout your selection and implementation. Make your selection based on your organization's unique situation, and you will not go wrong.

Toby Miller is a senior analyst with Enterprise Management Associates in Boulder, Colo., a leading analyst and market research firm focusing exclusively on all aspects of enterprise management. He focuses on storage management and the growing storage networking technologies. With over 20 years in the IT industry, Toby has experience in many areas of technology including product development, marketing, technical research, software implementation, and technical architectures. He can be reached at tmiller@enterprise
management.com

SCSI Trade Association

Adaptec

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