SAN speeds increasing, but demand questioned

Choose the fastest storage area networks available if the upgrade is going to cost you little, even if you don't need it right now, suggests IDC Australia storage analyst Graham Penn.

Choose the fastest storage area networks available if the upgrade is going to cost you little, even if you don’t need it right now, suggests IDC Australia storage analyst Graham Penn.

Fibre channel, the dominant technology used in SANs, is edging towards 4Gbit/s capacity as hardware vendors look at enabling their products, but Penn says most users have little need for such speed.

“To a degree, the demand for 4Gbit/s is not obvious. Most users went from 1Gbit/s to 2Gbit/s in the past 18 months because makers of 1Gbit/s equipment end-of-lifed their products.”

That transition didn’t cost users and Penn says if similarly seamless upgrade paths to 4Gbit/s become available, users should upgrade, even though they don’t need it.

“You’d be lucky if 1% of all organisations are taxing the limits of 2Gbit/s fibre channel. The only thing that arguably gets near taxing 2Gbit/s is streaming video and even a big file in a short burst doesn’t become a bottleneck.”

Most users are nowhere near saturating 2Gbit/s, he says, “and you’d only go to 4Gbit/s if vendors of HBAs [host bus adapters] forced you by end-of-lifeing 2Gbit/s. It’d be a technology transition from the supply side, not the user side.”

From a technology perspective, upgrading to 4Gbit/s is “a no brainer, because it’s backwards-compatible with 1Gbit/s and 2Gbit/s”.

Some are even talking about a medium-term transition to 8Gbit/s, “and my understanding is that would also be backwards-compatible”.

Talking about 10Gbit/s is probably premature.

“A year ago, my US colleagues regarded 2Gbit/ as the standard, 4Gbit/s was coming through and they didn’t see the need for it. They saw 10Gbit/s as the next big step, but it’s not backwards-compatible [with 1Gbit/s and 2Gbit/s].

"However, as users are unlikely to mix 10Gbit/s gear with 1, 2 or 4Gbit/s, that hardly matters. With 2Gbit/s hardly being stretched by most SAN users, talking about 10Gbit/s is getting esoteric, Penn says. “It’s a war of words between fibre channel and IP storage.”

The fibre channel camp saw a need to get to a 10Gbit/s standard to match 10Gbit/s ethernet, he says, as ethernet is the basis of IP storage standard iSCSI.

However, “it won’t be a user issue any time soon”. Bob Zona, optical modules marketing manager at Intel, recently wrote that “by 2006, most fibre channel hardware will ship with 4Gbit/s interfaces”, and noted that manufacturing 4Gbit/s optical SAN transceivers will be no more expensive than making 2Gbit/s gear.

Contradicting Penn, he also wrote “as IT managers deal with an ever-increasing deluge of data from emerging bandwidth-intensive graphics and video applications, and new document retention and security requirements, they will need to increase fibre channel SAN capacity without increasing costs”.

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