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Rein in NAS with file virtualization

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File virtualization checklist

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Five items to consider before you select and implement a file virtualization appliance.
  1. In-band or out-of-band? In-band file virtualization appliances present a common, single interface for all network file servers. While they can simplify management and file migrations, in-band appliances can become a bottleneck if not sized appropriately. Administrators can usually deploy out-of-band file virtualization appliances with little or no initial disruption to their environment, but they may need to push out agents to servers or move in-band to perform file migrations.


  2. Global namespace. A global namespace is a central catalog of the files that reside on network file servers. Organizations that have NAS namespaces may need to switch from their current namespace to the one introduced by the file virtualization appliance.


  3. Appliance availability. If you plan to use a file virtualization appliance strictly to perform file migrations, availability isn't a concern because both in-band and out-of-band appliances permit failures without data loss. But if you're planning to permanently virtualize the environment and also take advantage of advanced functions like striping files across different file servers or aggregating network filer volumes, make sure the appliance's level of availability matches your company's service-level agreements.


  4. Filer volume sizes. File virtualization appliances are often used to consolidate file systems residing on multiple network file servers onto one file server during migrations. However, it's important to remember to keep file-system volumes at sizes that can be backed up within specified backup windows.


  5. Support for network filer APIs. File virtualization appliances don't diminish the value that NAS operating systems like EMC Corp.'s DART and Network Appliance Inc.'s Data Ontap deliver with such features as snapshots and file locking. When using these features, look for file virtualization appliances that integrate with these devices so policies may be set on the appliance to centrally manage these functions.

Next steps
To transition their products from virtualization/migration engines to "corporate file managers," vendors are adding key features that will keep file virtualization appliances relevant regardless of how a corporation's NAS infrastructure evolves. File virtualization appliances, for example, allow organizations to index their corporate files and to immediately know when changes are made to specific files. Attune Systems recently established a relationship with Google to allow users to perform more sophisticated indexing and searching across their corporate file servers.

File virtualization appliance vendors also recognize that user storage environments will remain heterogeneous. "In these environments, our file directors act like an umbrella, allowing the free movement of data between different brands of network file servers," says Ali Zadeh, chief operating officer at NeoPath Networks.

Acopia Networks recently released the results from an independently validated lab test that demonstrated the ability to create a consistent point-in-time snapshot across a virtualized volume whose physical files simultaneously reside on both an EMC Celerra NS700 filer and a NetApp FAS3050 filer. The Acopia Networks snapshot was also used to create a self-consistent backup across multiple file servers.

"The ability to do snapshots across the proprietary boundaries created by many enterprise storage vendors is an important step toward the deconstruction of monolithic storage arrays," says Jon Toigo, chief executive officer and managing principal at Toigo Partners International LLC, an analyst firm. "Heterogeneous snapshot holds out the possibility of driving down the cost of array products by eliminating a consumer lock-in," he says.

EMC anticipates users will deploy Rainfinity for a broader range of applications. While migrations are now the primary use for Rainfinity, companies may also use file virtualization appliances for capacity, file, tiered storage and performance management. But according to Jack Norris, EMC's director of virtualization marketing, the real value of file virtualization appliances is that "virtualization will drive the intelligent placement and classification of data."

File virtualization appliances are a corporation's best bet when migrating files or optimizing file placement on network file servers. However, key differences in their architectures may narrow users' choices (see "File virtualization checklist," this page). IT shops with centralized, high-volume NAS implementations will largely start and stop their product search with Acopia Networks' ARX6000. Department-level and smaller IT shops will have the luxury to choose between in-band and out-of-band architectures. And if you're looking to use file virtualization appliances on a more permanent basis, you should give preference to products that are further down the road toward delivering a standardized approach of enterprise file indexing and search capabilities.

This was first published in March 2007

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