This article can also be found in the Premium Editorial Download "Storage magazine: Expanding SANs: How to scale today's storage networks."
Download it now to read this article plus other related content.
| Another way to
manage a lot of files
Is NAS a better alternative?
In the world of storage as elsewhere, there are many different ways to skin a cat. And if it's file sharing that's your trouble, there are a lot of people out there that will argue that NAS is still your best bet.
That may be especially true these days, with several new technologies on tap that address the limitations of traditional NAS systems. Startups such as NuView Inc., Houston, TX, and Z-Force, Santa Clara, CA, for example, both offer software that can aggregate a NAS environment into one coherent view. And then there are NAS startups such as Isilon Systems Inc., Seattle, WA and Spinnaker Networks, Philadelphia, PA, run their proprietary NAS boxes on top of 64-bit clustered file systems. In Spinnaker's case, users can cluster 512 of its NAS boxes together in a single 11PB file system.
IBM's Truskowski, however, is dismissive of NAS for demanding environments. "The performance is lousy," he says. Assuming Gigabit Ethernet as your connection, you're moving data half the speed of today's 2Gb/s FC networks. "There's definitely a place for NAS," he says, "but trying to solve these sorts of problems with it is like sending out a corporal to do a general's job."
But for some industry observers, that's all bluff and bluster designed to support a technology that has a questionable role to play in the average enterprise data center. "There's no question that if Almaden [the IBM research lab where Storage Tank was developed] had come up with the idea for Storage Tank today rather than five years ago, it never would have been built," says one industry observer who asked not to be named. But as it stands, "there are people whose entire careers depend on it," he says. "They're going to shine this pig up and bring it out to the party." For this source, who is a veteran of the distributed file system world, the cost and complexity that SAN FS brings to an environment far outweigh its purported benefits.
ESG's Kenniston meanwhile, has a far rosier view of SAN FS' future--but that future is much farther out than IBM may have you believe. "If you look at the future, it's all about Linux-racked servers, morphed with some sort of [Veritas blade management software] Jareva, running Oracle 9i RAC, on top of a clustered file system. That's the future." But he adds, "That's another two to four years away."
When it comes to blade computing, Joaquin Ruiz, vice president of marketing at Sistina Software Inc., Minneapolis, MN, agrees with Kenniston that clustered file systems are critical to the evolution of blade computing. "In the '90s, the main reason for using clustered file systems was high availability, not performance," he says. But with the advent of blades, "you no longer have just one or two monolithic servers connected in the SAN--you have dozens," and the clustered file can act as "the control point" that lets you manage it all.
However, Sistina, like its competitor PolyServe Inc. in Beaverton, OR, eschews SAN FS' asymetric out-of-band metadata architecture, instead choosing to distribute metadata symmetrically on all the nodes in the cluster. That approach, says Michael Callahan, PolyServe founder and CTO, is similar to the one used in "classical VMS clusters," from now-defunct Digital Equipment Corporation, and is much better suited to the high-performance transactional applications that many companies envision running on their blade servers. If other clustered file systems that rely on an out-of-band asymetrical architecture are any indication, he says, it is questionable whether IBM's SAN FS will be able to deliver the performance and high availability requirements put forth by blade applications such as parallel databases.
iSCSI and Ethernet are two other factors that could figure into when and how clustered file systems get deployed. Says Paul Ross, director of storage network marketing at EMC: "Go out three years--Ethernet's at 10 Gig, and more people are running iSCSI than not. At that point, SAN file systems start to make a lot of sense because you don't have to deploy a separate infrastructure to run them. The SAN file system becomes a LAN file system."
But what about today? Is SAN FS the answer to storage managers' file storage needs? In large environments, quite possibly, says ESG's Kenniston. But he cautions, "In the IT world, there are the haves and the have-nots. This is for the haves."
This was first published in November 2003