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Host-based software has been the most often-used tool to migrate data. It's best for application-specific migrations such as platform upgrades from Microsoft Exchange 2003 to Exchange 2007, and for database replication and simple file copying. Host-based software such as Symantec Corp.'s Veritas Volume Manager or Brocade Communications Systems Inc.'s StorageX frees the storage array of processing and eases data migrations between heterogeneous storage. It's also more economical than other tools for small-scale migrations, but can become problematic when lots of systems are migrated. Other examples of host-based migration software are IBM Corp.'s Softek Transparent Data Migration Facility, which runs on z/OS, Unix, Linux and Windows servers; Quest Software Inc.'s Storage Consolidator for Windows; and Symantec's Veritas Volume Replicator. All of these software packages can be used to migrate volumes, files or blocks of data.
Array-based software is primarily used to migrate data between homogeneous storage devices and to reduce the impact on host computer operations. Users will likely choose array-based software to move data between generations of a vendor's product. Examples include EMC Corp.'s Symmetrix Remote Data Facility, IBM's Peer-to-Peer
| Remote Copy and Compellent's Storage Center Thin Import
The scope of array-based software has recently changed. Hitachi Data Systems now offers a controller-based virtualization product with its TagmaStore array that supports the migration of data between Hitachi and non-Hitachi vendor arrays. EMC offers Open Replicator for Symmetrix.
The third type of migration tool used is a network appliance like F5 Networks' Acopia ARX Series switch, Brocade's File Management Engine or Sanrad Inc.'s V-Switch. These devices migrate volumes, files or blocks of data depending on their configuration. For example, the Acopia ARX Series switch migrates file-oriented data between NAS devices and file servers, while the Sanrad V-Switch migrates lock-oriented data.
With a network-based appliance, performance can be improved by aggregating and balancing the migration load across the filers, says Oversee Domain Services' O'Neill. In addition, "if I want to take a filer out of operation for a firmware upgrade, I can migrate the data off the filer, pull the filer out from the back of the Acopia, do the firmware upgrade, put it back in and migrate the data back. There's no disruption to the application," he says.
This was first published in June 2008