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Report: SANs and the City

One thing companies don't lack these days is data. The CEO may be headed for the clink and the budget squeezed bloodless, but there's no lack of information on corporate networks, particularly as new regulations have companies saving even more documents in case the SEC comes calling.

Keeping all of that info flowing freely, particularly in metropolitan area networks (MANs), is a growing challenge, and the subject of a report just posted on Byte and Switch.

SANs are increasingly vital to coordinating and consolidating data, according to SANs on MANs, by analyst Chris Murton of Murton Consultancy & Design Ltd. Until recently, though, they didn't travel well. Fibre Channel, the block-oriented data transport technique used in most big SANs, supports distances up to 500 meters on multimode fiber and 10 km on singlemode. But many large enterprises span multiple sites within big urban areas -- ones that can extend beyond 20 km.

SAN extension has come to the fore as a way to ensure companies that have chosen SANs can send data where they want, when they want. There are three main techniques: Wavelength Division Multiplexing (WDM), including coarse or dense; Sonet (Synchronous Optical NETwork) and SDH (Synchronous Digital Hierarchy); and Internet Protocol (IP). Each has its particular niche. WDM, for instance, offers the highest performance and bandwidth over short distances for data that must be continuously available in case a system fails, such as financial transaction records. IP may be best suited to data that can be spared for a few hours if a system goes down. Sonet/SDH fits most applications that require average accessibility in case of downtime, though WDM may actually be a more scaleable option if higher bandwidth is required.

A range of companies specialize in SAN extension or have made SAN extension a key element of their optical metro gear, including:

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