'Grid' storage is in the eye of the beholder (and vendor)

Storage Networking World - Greg Bosworth, Jess Carruthers and Mike Luter are all testing or deploying grid storage to hold down costs, streamline backups and restores or make storage administration easier.

But none of them went shopping for grid storage per se. To them, grid storage is a useful technology for solving specific problems but not a new product or technology in its own right.

"It doesn't matter to me if you hook it together with glass or copper, or if it's red or blue," says Carruthers, who last year consolidated 10 Network Appliance 800 Series filers into a single FAS960 cluster running NetApps' Data ONTAP 7G storage software. "The functionality is what you need."

As vendors promote differing visions of "grid," customers and analysts urge users to evaluate products based on the benefits they deliver today. Among the benefits customers should look for is how much a grid architecture will reduce the upfront costs of buying storage, how it will ease backups and restores, how it will make it easier to reallocate storage as needed, and whether the grid can support both block- and file-level access.

The storage grid
Grid storage is an architecture in which independent storage nodes are linked and governed by common control software. That control layer provides a single management interface and fault tolerance among the nodes, as well as the ability to access either file- or block-level storage. It also makes it possible to easily or even automatically reassign nodes to different functions, such as from online to archival storage, as needs change.

"As you need capacity, you add a node to the grid, and they self-configure and become part of an entire pool of storage," which greatly reduces storage management costs, says Stephanie Balaouras, a senior analyst at the Yankee Group.
That's the ideal. In the real world, different vendors offer different grid capabilities, sometimes packaged as "clusters" or "virtualized" storage. Virtualization means managing separate physical storage pools as one virtual pool, which is often one of the capabilities provided by grid storage.

In a storage cluster, the nodes are networked as in a grid, but they all generally support the same application or function. This is different from a grid, where each node can ideally be reconfigured for different purposes. Then there is storage for grid computing, in which the storage is not necessarily linked in a grid but is optimized for processors linked in grids for high-end scientific and technical applications.

Various vendors use combinations of these technologies to deliver the flexibility, manageability, performance and data protection promised by grid storage.

Different vendors, different grids
If storage nodes linked by a network sounds an awful lot like a SAN to you, you're right, as SAN vendor EMC Corp. is quick to point out. "You could argue that Celera, which is a cluster of file servers, is a grid," says Rick Strom, director of NAS product marketing for EMC. While EMC is paying close attention to evolving grid architectures, Strom says the company is trying to figure out what problems the architecture solves rather than market grid technology as a benefit in and of itself.