Cruising Over Copper

Ethernet over copper cabling promises to lower costs for high-bandwidth storage.

Just when it looks like Fibre Channel is the clear choice for high-bandwidth networked storage, trusty old Ethernet gets a performance boost that makes iSCSI a viable competitor when it comes to sheer data-transfer speed.

The latest IEEE specification for 10 Gigabit Ethernet (802.3an, if you're keeping track), also known as the 10Gbase-T standard for unshielded twisted-pair Category 6 copper cabling, is expected to be ratified this summer.

While the existing Ethernet spec for copper cabling, 802.ak, or 10Gbase-CX4, will run up to only 15 meters, 10Gbase-T will run up to 55 meters over Category 6 untwisted-pair cable and up to 100 meters over shielded twisted-pair cable.

Although the new spec won't change the landscape of networked storage, it should allow Ethernet- and IP-based storage to solidify its place in business.

The latest 10 Gigabit Ethernet specification will be finalized just as the market for the high-bandwidth form of the networking technology gains momentum. Dell'Oro Group Inc. expects the 10 Gigabit Ethernet market to grow from $1.8 billion in 2006 to $4 billion in 2010. The research firm also forecasts 10 Gigabit Ethernet port shipments to grow from 854,000 in 2006 to almost 10 million in 2010. Meanwhile, the average selling price for the switches is expected to drop from $5,200 to just over $400 during the same period.

At least in the near term, Fibre Channel will continue to be the protocol of choice for transaction-heavy networking associated with storage-area networks (SAN). But three factors could help make IP-based storage using iSCSI an attractive low-cost alternative to Fibre Channel in SANs and other shared storage architectures: the plummeting cost of 10 Gigabit Ethernet ports on both servers and storage arrays, the fact that IP-based storage is less complex than Fibre Channel, and an abundance of on-staff expertise in IP and Ethernet in IT departments.

"Choosing Fibre Channel over Ethernet in the data center has been perfectly logical, but now Ethernet is keeping pace with Fibre Channel's continuing performance improvements," says Sal Capizzi, an analyst at Yankee Group Research Inc. "Fibre Channel is currently at 8Gbit/sec. and will be up to 10Gbit/sec. in late 2007. Customers who are considering iSCSI can now be assured that it won't be outpaced by 8GB Fibre Channel."

All the reasons for using iSCSI -- especially low cost and simplicity -- are reinforced by the new specification. Throughput speeds of up to 10Gbit/sec. make the IP-based standard suitable for smaller organizations that don't have the resources or expertise to deploy Fibre Channel, as well as larger companies with substantial investments in Ethernet, says Capizzi. "The chief benefit to implementing 10 Gigabit Ethernet will be for applications that require high bandwidth for continuous data flow, such as traditional backup to tape, disk-to-disk backup, data archiving and data replication for disaster tolerance," he says.

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