De-dupe can be done at the target of a backup stream (the storage array or tape drive) or at the source of the data being backed up (the application server). Traditionally, de-dupe products had been used as a target for backup data, but Schulz says there is "a growing emphasis de-duping back on the server."

Target de-dupe products are generally used as part of a final repository for backup data. Most backup software today supports tape volumes, files or raw disk as targets. Target de-dupe products mimic a tape library and support virtual tape libraries (VTL), or they can act as a network-attached storage file server supporting network file system (NFS) or Common Internet File System files. Target de-dupe technology can also work on raw disk supporting Internet SCSI or Fibre Channel logical unit numbers (LUN). Prominent target based de-dupe products are sold by Data Domain Inc., Diligent Technologies Corp., ExaGrid Systems Inc., FalconStor Software Inc., Quantum Corp., and Sepaton Inc.

Today, de-duping data at the target is the leading method, but de-duping data at the source where the data is coming from is even more disruptive, and the benefits are far greater, Schulz says.

Source de-dupe products replace backup software used in a client/server configuration, where remote clients de-dupe data being backed up and only transmit unique data to the central server. This reduces bandwidth requirements considerably, according to Schulz. Some prominent source-based de-dupe products include Asigra Inc.'s Televaulting for Enterprises, EMC Corp.'s Avamar, Network Appliance Inc.'s SnapVault, and Symantic Corp.'s NetBackup Pure Disk.

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