Feature

Easing away from ESCON

In 1999, IBM began selling FICON, the mainframe equivalent to the Fibre Channel Protocol (FCP), as a way to connect mainframe systems to disk and tape storage devices. Following in FCP's footsteps, the company is expected to announce 4Gb/sec FICON in 2006.

But ESCON, the protocol that pre-dated FICON as a systems-to-storage connection, is tenacious and still figures prominently in many mainframe shops, says Greg Schulz, senior analyst at the Evaluator Group Inc., Greenwood Village, CO. "There's still quite a bit of ESCON out there," he says, on devices like disk arrays and tape libraries, as well as on peripherals like printers, check sorters and even ATM machines.

On paper, migrating from ESCON seems like it should be a no-brainer. ESCON runs at 17MB/sec vs. FICON's 200MB/sec. From a disaster recovery standpoint, FICON channels can be natively extended to 100km, but ESCON's reach is only 3km. ESCON supports far fewer device addresses than FICON. Then there's the question of maintenance and support. IBM has end-of-life'd ESCON, and while it still supports it, the cost of maintaining and supporting older equipment can be prohibitive.

"Customers have a dilemma," says Brian Larsen, director of product management for storage networking at McData. "They want to take advantage of things like increased port density and port consolidation on the host, but their ESCON stuff is working fine and it's paid for."

ESCON may not be broken, but it is incompatible

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with the newer FICON-based systems that many users have upgraded to. For that segment of the mainframe population, storage networking equipment vendor McData is now selling the Intrepid FICON Converter (IFC). Based on Optica Technologies' Prizm module, the 2U-high rack-mount device supplies one or two FICON channels and up to 12 ESCON channels, and allows you to connect an ESCON-attached tape device to a newer host.

That's the most common scenario today by far, says Mario Blandini, product marketing manager for enterprise products at Brocade. "There's often a large tape library asset [the company] has not depreciated and that they'd like to leverage with a new [FICON-based] zSeries," he says. Last month, Brocade announced its new 4Gb/sec SilkWorm 48000 director, which supports Fibre Channel and FICON, but not ESCON.

So far, McData's IFC does nothing for environments with ESCON-attached disk and a FICON host. Nor does it address the problem of trying to pair an older ESCON-based host with newer FICON storage devices. According to Larsen, Optica has a version of the product on its roadmap that would cater to those environments.

"At this point, we see more people trying to migrate the hosts first, then the storage; but there's really no right way to do this," he says.

This was first published in November 2005

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