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
About the author: Alan Earls is a freelance writer in Franklin, Mass.
This was first published in July 2004