There's a flip side to building SANs and NAS

By Kevin Komiega, Assistant News Editor 02 Nov 2001 | SearchStorage

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Amid times of financial belt-tightening, IT budgets are on the chopping block and IT professionals are left with the task of figuring out how to do more with less.

According to storage expert Marc Farley, who spoke to a crowd of more than 400 top-level storage professionals at the Storage Decisions 2001 conference in Chicago in September, it's time to come up with a new method for understanding and analyzing storage network products and technologies. That means leaving behind conventional concepts of storage area networks (SANs) and network-attached storage (NAS).

Farley believes storage can be broken down into three categories: wiring, storing, or filing.

"Isolating these three functions makes it possible to cut through the propaganda that inevitably occurs when vendors or industry groups vie for market share," he said. "All storage networking products can be broken into these three functional components."

As Farley refers to it, wiring is made up of the transport technology used, whether it is bus technology or networking and includes software components as well as network/bus hardware and cabling.

Filing provides the structure for storage, he said. These can be external representations of storage in folders and directories or they can be the data structures on storage devices and volumes that are used by the system to manage access to data.

And finally, storing involves the obvious: RAID, mirroring, volume management and device virtualization.

Farley said storage could be thought of as an application with two major parts: logical block storing and file storing. Both can travel over any kind of wiring. "I believe there will be a convergence of technologies, but not necessarily of the same physical network paths. Storage needs its own path to keep latency and errors to a minimum," he said.

He said that at some point there might be more categories as the file systems get broken down and distributed.

Farley said the problem with SANs is that it only tackles the application of storing. "There's no knowledge there, just blocks and bits and no data structure," said Farley. "The structure is provided by the file system that resides somewhere else."

That's where NAS comes in, he said. "NAS is the application of filing functions over a network, but it has not been historically reliable enough to do high [input/output]," Farley said.

The challenge for NAS is in the wiring or interconnect. "If the wiring is up to speed you can do anything with NAS," he said. "If not, it's suspect."

Filing, he said, is where the action is. If you do not have a file system that works with virtualization you won't have 24x7 availability, he said, virtualization is important, but it's hyped out.

The gatekeepers between the end-users and the root of the problem are the switch vendors, said Farley.

"The Fibre Channel industry has made it seem like error correction happens at the storing level," he said. "Servers and storage don't participate in the rerouting of data when there's a problem or failure in the network, the switches do," he said.

Farley said the end users need to pressure switch vendors into looking at new ways of routing.

Ultimately, he said, while data sharing in SANs is extremely difficult, it's going to improve. According to Farley, what's difficult is trying to correlate the management of wiring, storing and filing.

"Management is a part of all three," he said. "Software and management tools are going to make a big difference in storage going forward."

Farley said storage is due for an adjustment. "The market is slowing because storage is a discretionary purchase. As money gets tighter, storage experiments are going to slow. It will hurt SANs more than NAS, but all parts are seeing the fallback," he said.

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