Ten Gigabit Ethernet -- the latest and fastest version of the ubiquitous data networking protocol -- is also coming to the networks that link storage arrays to each other and to servers.

Questions yet to be answered include: How quickly will iSCSI networks running 10 Gigabit Ethernet hardware become mainstream? Which applications will it be used in? And how much of the high-end storage market will be left for Fibre Channel (FC), which is now the protocol of choice for applications which require the very fastest, most reliable storage?

"Over time, things like even mission-critical applications will be run on iSCSI," says Larry Hart, a senior manager in the storage and networking group at Dell Inc. "More and more customers are starting to say yes" when asked if they would trust transactional applications and the like to the protocol, he says.

According to this view, the eventual lower cost of 10 Gigabit Ethernet hardware, combined with the easy availability of trained Ethernet administrators, makes it likely that most companies will eventually run a single, combined data and storage network on Ethernet.

Others insist Fibre Channel is far from dead. They argue 10 Gigabit Ethernet running on iSCSI is still unproven for the most mission-critical applications. They also question how many applications need that much throughput and point out that 10 Gigabit Ethernet will require costly switch upgrades or network interface cards until servers ship with 10 Gigabit Ethernet ports.

But there's one thing everyone agrees on: 10 Gigabit Ethernet will bring major changes to the way organisations buy and manage their storage networks.

While it is only now gaining visibility in the storage world, 10 Gigabit Ethernet was ratified in 2002 and is already in use in many data networks. One delay is due to the fact that running just Gigabit Ethernet means most transactional applications don't face network bottlenecks.

However, some users are buying 10 Gigabit Ethernet switches to speed traffic among switches at the core of their networks, known as interswitch links, which otherwise would slow under all the data coming over multiple Gigabit Ethernet links. Internet service providers, application service providers and storage service providers are among those who need the 10Gbit bandwidth at the core of the network for applications such as remote replication and disk-to-disk backup.

Also guaranteed to benefit from 10 Gigabit Ethernet are applications such as video editing or scientific applications that consume or generate huge amounts of data in a short time.

Within data and storage networks, the adoption of iSCSI at any speed has mostly been limited to "tier 2" applications such as decision support, say some observers. The lack of mature and necessary features such as snapshots means "a big Fortune 1,000 bank is not going to trust an IP SAN with its core data," says Jeff Whitney, vice president of marketing at Intransa, an IP SAN vendor in San Jose.

But others don't hold that view. For example, Brian Garrett, an analyst at Enterprise Strategy Group, says iSCSI is in fact being deployed "for Tier 1 and Tier 2 apps in companies of all sizes." He also sees a future market in using 10 Gigabit Ethernet to connect many blade servers to shared storage.

"Lots of blades sharing a fat connection to shared storage saves costs and reduces complexity," says Garrett.

Currently, the required NICs cost about $550 per port, says Jay Kramer, vice president of marketing at iStor Networks, an iSCSI storage vendor in Irvine, Calif. That price is roughly equivalent to a 4Gbit/s host bus adapter needed to connect servers to storage using Fibre Channel. As prices fall, 10 Gigabit Ethernet will become a stronger option, says Garrett.

Market Forces

Garrett expects that for the next few years, Fibre Channel will have a price edge over 10 Gigabit Ethernet, but beginning about three years from now 10 Gigabit Ethernet hardware will reach "commodity" price levels, he says.

"With its price/performance advantage over 4Git/s Fibre Channel, 10Gbase-CX4 [which runs to more than 15 yards over coaxial cable] is the ideal candidate for uplink bandwidth aggregation" in SANs for next several years, says Kramer. At that point, he says, 10Gbase-T (which can run to more than 55 yards over lower-cost untwisted-pair copper) will be the protocol of choice.

As for pricing, a Hewlett-Packard ProCurve 6400cl-6XG 10Gbase-T six-port switch goes for about $3,400, which comes to about $567 per port. Pricing for a single port 4Gbit/sec. Fibre Channel HBA runs from $880 to $1,360 per port. So, 10Gbase-CX4 is currently about half the price of 4Gbit/s Fibre Channel as a server interconnect.

On the switch side, which is where it would be used for uplink bandwidth aggregation, a 10Gbase-CX4 HP switch retails for about $600 per port compared with about $780 per port for a 4Gbit/s Qlogic Fibre Channel switch. That's still a big difference, but not as large as the one on the server side (Note: Pricing information was found through simple Web searches, not vendor information).

Users might save more on administration than on hardware costs, since there's a far larger supply of network administrators trained in Ethernet than in Fibre Channel, observers say.

Another plus for iSCSI over Ethernet is that it is "an ideal environment" for virtualisation, says Hart, because it allows administrators to move virtual servers among physical machines without reconfiguring the zoning and logical unit number (LUN) masking in the storage network.

Taufik Ma, vice president of marketing for intelligent network products at Emulex, a storage connectivity vendor in Costa Mesa, Calif., says most iSCSI adopters tend to be those who have not yet invested in Fibre Channel. While some claim 10 Gigabit Ethernet is best suited for customers with no Fibre Channel investment to protect, others see it co-existing with or even replacing Fibre Channel.

10 Gigabit Ethernet tips

Some end users have "dipped a toe in the iSCSI market using a router in their FC director," says Garrett. "This enables them to leverage what they have in the FC SAN and connect it to Tier 2 apps, test and development servers, and servers outside the reach of the Fibre Channel infrastructure."

Patrick Cimprich, chief architect of infrastructure and security solutions at Avanade, an IT consultancy in Seattle, advises users to manage Ethernet storage networks as carefully as a Fibre Channel network. That includes segregating storage traffic from data or voice traffic and maintaining the strictest change control over servers and switches at the core of the network where bandwidth demands are highest.

Others advise carefully choosing the type of drives to deploy. Although desktop-class serial ATA (SATA) drives have "extremely attractive pricing, the throughput and IOPS of enterprise-class SATA drives are about 25 percent higher," says Kramer. And while the performance of SATA drives may come close to that of Fibre Channel drives in sheer throughput and reliability, Fibre Channel drives are still better at handling "random access and on servicing multiple parallel requests," says Cimprich.

Even if one staff manages both data and storage networks, organizations will still need a dedicated storage administration staff to create and manage storage volumes, LUNs, snapshotting and volume copies, says Hart. The network manager will handle jobs such as creating virtual LANs for storage traffic and ensuring that there is enough bandwidth for storage, he says.

Eventual Triumph?

"Over the last 12 months, we've seen a shift from companies who say, 'I've got Fibre Channel, and I'm going to stick with Fibre Channel' to companies saying, 'Wow, this is a pretty compelling story for iSCSI and we are considering mixed iSCSI/Fibre Channel environments,'" says Cimprich.

Whether its victory is complete or only partial, it seems inevitable that 10 Gigabit Ethernet is here to stay in storage networks.