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Technologies that can help with NAS sprawl

The industry took note and recognized this sober situation. The result is the current availability of four technologies designed to solve some or all of these challenges, albeit in completely different ways. They include: operating system built-ins such as Microsoft's Distributed File System (DFS) for CIFS as well as Linux/Unix automounters for NFS; file virtualization systems; clustered NAS systems; and private cloud and grid storage. A brief analysis of each of these technologies illustrates what they do and don't do to meet the aforementioned challenges.

1. Operating system built-ins

Microsoft Distributed File System (DFS) is part of Microsoft's Windows 2003 and 2008 server operating systems; DFS was developed for the small- and medium-sized business (SMB) Windows-only (CIFS) market. DFS Namespaces enables multiple file servers' shared folders to be grouped into one or more logical namespaces. Users see the namespace as a single shared folder and are automatically connected to shared folders in the same available Active Directory domain services site. This sidesteps the need for LAN or WAN routing. DFS Replication can automatically synchronize folders between local file servers or remote NAS systems on a wide-area network.


  • Easy integration with Windows environments
  • Familiar to Windows

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  • administrators
  • No additional licensing costs
  • Low upfront total costs
  • Solves user access, mount/unmount, load balancing, data migration as well as some data protection challenges of multiple CIFS NAS systems


  • Requires a relatively high level of Windows expertise
  • Loose file synchronization among different servers, especially when geographically dispersed; a user at a remote location may access a file before it's updated
  • Only works with CIFS (not NFS)
  • Limited scalability; not architected to scale to large numbers of file servers
  • Doesn't provide file-level granularity
  • Doesn't work with non-Windows-based NAS systems
  • Poor storage utilization because of large numbers of duplicate files
  • Can require additional hardware infrastructure to meet performance requirements
  • Doesn't solve issue of managing multiple NAS or filer systems; doesn't address data migration and many of the data protection challenges

Linux/Unix automounters are intended for NFS users. Automounters mount and unmount directories from other systems on the network as they're needed. They get their mounting instructions from centralized maps, which can be flat files, NIS maps or sections of an LDAP directory. Automounters are far easier to use than managing multiple static NFS mounts. Automounter advantages are readily apparent when there's a service failure. If a remote file server becomes unavailable, an automounter will simply time out and unmount the directory without alarming users. With static NFS, mounts will hang until the file server is back up and running again.


  • Easy integration with Linux and Unix environments
  • No additional licensing costs
  • Low upfront total costs
  • Eliminates server hangs when the mounted service fails
  • Works in conjunction with most NFS NAS systems
  • Solves many of the user and mount issues with multiple NFS NAS systems


  • Requires significant Linux or Unix expertise
  • Not easy to set up
  • Only works with NFS
  • Lacks built-in replication capabilities
  • Doesn't work with Windows (CIFS)-based NAS systems
  • No file-level granularity
  • Doesn't solve many of the management problems with multiple NAS systems

This was first published in February 2010

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