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Dueling SAN technologies: NAS vs. iSCSI

Competition between the two "budget" storage technologies is heating up.

What you will learn from this tip: The relative merits of iSCSI and NAS technologies as alternatives for Fibre Channel-based SANs.

Although Fibre Channel (FC) SANs continue to attract customers, storage professionals have never stopped looking for other, cheaper and less complex technologies. ISCSI is the most recent blip on the radar screen. But now that iSCSI products are finally coming on to the market, many analysts see the competition shaping up not between Fibre Channel and iSCSI, but between iSCSI and the other traditional "budget" approach to storage networking, Network Attached Storage (NAS).

The major difference between iSCSI and NAS, says Randy Kerns, senior analyst with Greenwood Village, Colo.-based Evaluator Group, is that, like FC, iSCSI handles data in blocks while NAS moves it in files. Applications that lend themselves to block-based I/O, for example Microsoft SQL and Exchange, are ideal candidates for iSCSI (though Exchange now works under Windows Storage Server-based NAS). On the other hand, file-based applications have the advantage of lower administrative costs if they are used over NAS.

"When you have an iSCSI solution, you still have the same administrative issues as with a Fibre Channel SAN -- things like LUN creation, for example," says Kerns. The only advantage over FC, from a storage administrator's standpoint, is that you can share a network administrator with other network functions.

But that can be a double-edge sword, Kerns adds. "In a typical enterprise data center, the people that manage the storage networks in that environment are not the same network people that deal with IP, so you could end up with a sociological problem," he says. In small and medium-sized businesses, there usually isn't a dedicated storage professional, so it doesn't make any difference.

The cost issue is primary, says Kerns. Customers who deploy iSCSI often do so where they need block storage, or for connecting "stranded servers" that have no connection to the data center. "People only have to add an iSCSI or a multi-protocol router," he says.

Michael Karp, senior analyst at Boulder, Colo.-based Enterprise Management Associates agrees, says that both iSCSI and NAS represent very viable options for those with budget sensitivities and both should be easy to manage. What's more, Karp says the old complaint that NAS was "easy to manage but hard to scale" no longer holds true with today's more sophisticated NAS products, leaving both as viable options for a wide range of storage networking applications.

For more information:

Tip: Next-generation NAS

Tip: How to decide between Fibre and SCSI SANs

Tip: Is low-cost Fibre Channel finally here?

About the author: Alan Earls is a freelance writer in Franklin, Mass.

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