By Dave Simpson
Paralleling an effort by IBM and Cisco (see story on this page), Adaptec has submitted to the Internet Engineering Task Force (IETF) a proposed standard for running SCSI-over-TCP/IP networks such as Gigabit Ethernet. The goal of the proposal is similar to the IBM-Cisco effort, and most parties expect the various standards efforts to converge over the next few months.
Also participating in Adaptec's "EtherStorage" proposal are vendors such as 3Com, Hewlett-Packard, IBM, and Quantum.
"Our goal is to enable the use of cost-effective storage area networks in a broader market via Ethernet," says Mark Lohmeyer, marketing manager in Adaptec's storage networking solutions group. He says that target companies include cost-conscious sites and companies that have a large infrastructure built on Ethernet.
However, as with other efforts to run SCSI over TCP/IP networks to create Gigabit Ethernet SANs, reality may be a few years away. Nevertheless,
Adaptec plans to ship EtherStorage-compliant products in mid-2001, including a host bus adapter and a bridge product with an EtherStorage attachment on the front end and Fibre Channel or SCSI attachments on the back end. The technology was demonstrated at last month's Networld+Interop show.
Adaptec is positioning the SCSI-over-TCP/IP technology as being complementary to Fibre Channel SANs. "In the future, Ethernet-based storage and Fibre Channel will compete, but if you want to build a SAN today, Fibre Channel is the only way to go," says Lohmeyer. (Adaptec's Ethernet move comes shortly after the company re-entered the Fibre Channel market via a partnership with Agilent Technologies and the acquisition of DPT.)
Lohmeyer also says that Adaptec's proposal is complementary to the IBM-Cisco proposal. Both IETF groups are working on standardizing a SCSI encapsulation protocol. Functionally, the two methods are the same, but they differ in implementation. Both groups hope to agree on a single standard.
As with the IBM-Cisco SCSI-over-TCP/IP proposal, one big stumbling block is the poor performance of the TCP/IP stack. Lohmeyer says that there are two options to overcoming the stack overhead and CPU utilization problems. One is to implement the TCP/IP stack in hardware on network interface card (NIC) accelerators. The other approach is to use a lighter-weight transport layer that's optimized for storage traffic in a SAN environment. Tackling the latter option, Adaptec is developing a SAN transport protocol (STP) that would provide an alternative to TCP (see diagram).
"You could use different transport layers for different applications," says Lohmeyer. "For example, TCP/IP for WANs or an STP-like protocol for local SANs."