SCSI over TCP/IP
By ALEX WINOKUR
Network World, 06/12/00
Implementing SCSI over TCP for IP storage leverages existing network hardware, software and technical know-how. SCSI over TCP will enable the use of Gigabit Ethernet, a proven industry standard, as an infrastructure for storage-area networks (SAN). TCP/IP and Ethernet are dominant technologies in networking, and we see this trend continuing with SANs.
Using Gigabit Ethernet and SCSI over TCP offers significant economic benefits. The vast number of Ethernet equipment manufacturers, coupled with the technology's maturity, means Ethernet equipment will always be more readily available than Fibre Channel equipment and at a lower price. SCSI over TCP SANs also will be less expensive to support than Fibre Channel-based SANs, which require additional training for the IT staff. In addition, the limited number of management tools for Fibre Channel SANs means an IT department will have to spend more time supporting the network.
There are also technical advantages to deploying Gigabit Ethernet and SCSI over TCP SANs. SCSI over TCP will let companies use existing management platforms that provide advanced levels of support. TCP/IP and Ethernet have been around for decades, and duplicating their technical achievements is counterproductive. Fibre Channel's chief technical problem is that it is attempting to reinvent the wheel. Issues such as security and quality of service have already been dealt with (and continue to be improved) in TCP/IP networks, while Fibre Channel vendors are just beginning to scratch the surface.
Fibre Channel is the only viable solution for implementing a SAN until SCSI over TCP becomes available. Some Fibre Channel switch vendors are developing routers that will let Ethernet networks attach to Fibre Channel SANs. This will give customers a choice between deploying an end-to-end Fibre Channel SAN and using a router to minimize the amount of Fibre Channel that must be installed. Fibre Channel/Ethernet routers may be a decent interim solution, but they don't have long-term potential because extra overhead is added, encapsulating and de-encapsulating packets back and forth across the router. An end-to-end Gigabit Ethernet SAN using SCSI over TCP won't have this added overhead and therefore will outperform a Fibre Channel/Ethernet SAN.
Fibre Channel vendors argue that Fibre Channel is optimized for storage applications and provides much higher performance than the combination of TCP/IP and Ethernet. This is debatable, especially because TCP accelerators are being developed and TCP/IP stacks are being embedded in silicon.
Should you start planning for SCSI over TCP for your SAN? Consider the fate of other technologies that have attempted to compete with Ethernet, such as token ring and LAN-based ATM, and the answer will be clear.
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Winokur is vice president of engineering at SANgate Systems, a data storage management company in Southborough, Mass. He can be reached at alex@sangate.com.
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