NAS filers have become a fact of life in many enterprises. These storage appliances with their low initial cost and quick installation are a way to provide 'instant storage' to workgroups, branches and other parts of the enterprise.
However as NAS installations have grown, so have the problems of administering NAS devices. Each NAS filer is a stand-alone file system within the organization and storage administrators have found that the proliferation of filers has left an increasing number of files and folders in such standalone file systems. The problem becomes particularly acute as NAS filers fill up and additional filers have to be added to meet the growing storage needs of the departments that installed them.
One solution to the problem is make NAS more expandable. Today most of the major NAS vendors offer the ability to add storage to their NAS devices. In fact some of them are in effect NAS storage networks where the NAS filer serves as a front end to connect a storage network to the enterprise network.
Recently attention has focused on the idea of NAS aggregation; treating all the enterprise's NAS devices as a single entity. A number of vendors, including
The holy grail of NAS aggregation is a device which will virtualize every NAS device in the enterprise in the same way SAN virtualization does for SANs. In effect the enterprise sees a single large NAS device with all questions of location, individual capacity, etc., hidden from users and administrators. One way to do this is with a file switch, a hardware device that acts as a front end for all the NAS filers on the system, no matter where they are located or how they are connected. Among others, Zforce is developing a file switch and promises to have it on the market by the end of this year.
Among the immediately available products, the thing that comes closest to true NAS virtualization is the NAS gateway. Some of these devices, like Spinnaker Networks' SpinServer series, are designed to virtualize all the NAS storage behind them. Spinnaker's architecture includes a virtual file system to aggregate storage on all the devices connected to the gateway, a virtual server to present the storage resources to the enterprise network and a virtual interface to grant access to users or user communities.
It is possible to get some of the benefits of NAS aggregation without installing a new NAS architecture with software. File system aggregation, which presents a single logical view of all the files on the enterprises NAS filers, for example, considerably reduces day-to-day management problems.
One way to do this is to set up a global namespace for NAS filers by discovering which NAS appliances are on the system and collecting information about them to present as a single unified view. This is NuView's approach with its StorageX product.
Some products will not only provide a global view of NAS filers, they will allow shared storage across them. Unused capacity on the NAS devices is combined into a single storage pool to be allocated at need. 1Vision uses this approach with its vNAS product.
NAS aggregation is still developing rapidly and the products are quite distinct in their capabilities and limitations. Storage managers thinking about NAS aggregation should carefully consider their actual needs and compare those against the strengths and limits of the available solutions.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
This was first published in May 2003