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NAS heads: Gatekeepers for enterprise storage

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Managing files has become a big headache for enterprises. How should the files be stored, and on what tier of disk? And are there other considerations, such as legal regulations pertaining to the disposition of the files? Consolidating disparate NAS filers behind a NAS appliance gateway offers companies an effective way to scale file systems and manage back-end storage arrays, but it also creates its own set of problems. As NAS gateways move off the array and into the network, organizations must start to plan how best to use them.

A NAS head appears in the network in one of two ways. In the traditional sense, it ships as part of a larger storage subsystem with its own set of disk, such as Network Appliance (NetApp) Inc.'s FAS980, and as a standalone appliance, such as NetApp's gFiler that functions as a gateway to connect storage arrays of different tiers and even different vendors. These gateway products generally use Fibre Channel (FC) to connect to back-end arrays.

Using one central NAS head to consolidate existing NAS filers creates the following issues:

  • Performance may drop as more users access their files centrally.
  • Users may face network storage quotas for the first time.
  • Managing, cataloging and determining ownership of multiple versions of files with the same name but different access and modification dates.
  • Determining what type of disk the different types of data can sit on.

Support for the iSCSI protocol allows organizations to use NAS heads for file- and block-based services. The ability to dynamically re-stripe data across back-end arrays lets administrators optimize the performance of new and existing data. And as more NAS head vendors support and certify different vendors' arrays, users no longer need to lock themselves into a particular vendor's array. Many NAS head vendors now support multiple tiers of back-end storage along with policy management tools that allow aging files to be transparently migrated from one tier of storage to another. With so many options available, users need to distinguish between required and optional features on NAS heads. The must-have list includes:

  • Ethernet ports to connect servers
  • NFS and CIFS protocol support
  • Support of multiple tiers of storage
  • Policy-based management
  • Storage management functions such as snapshots and mirrors

In addition, organizations should consider the following features as they plan for the future:

  • iSCSI support
  • FC ports to connect NAS head gateways to external arrays
  • Support for multiple vendors' arrays
  • Dynamic allocation and extension of volumes and file shares
  • Ability to re-stripe data across back-end arrays
  • File sharing with remote offices
  • Global namespace

This was first published in March 2005

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