Storage Informer
Storage Informer

EMC Disk Library Adds Path To Tape

by on May.18, 2009, under Storage

EMC Disk Library Adds Path To Tape

EMC logo EMC Disk Library Adds Path To Tape

First up of several unique features that are being announced for the EMC Disk Library (DL) family this week is Path To Tape (PTT). The feature of adds significantly to the functionality of the DL1500 and DL3000 in NetWorker and…

First up of several unique features that are being announced for the EMC Disk Library (DL) family this week is Path To Tape (PTT). The feature of adds significantly to the functionality of the DL1500 and DL3000 in NetWorker and NetBackup environments.

Path To Tape effectively gives the two members of the DL family that lack the embedded storage node (ESN) and embedded media server feature exclusive to the DL4000, a way to achieve similar functionality. PTT gives NetWorker and NetBackup a way to instruct the DL1500 and DL3000 to create a tape with a directly attached tape drive that contains the same save sets as can be found on a virtual volume.

The use cases are pretty clear here, and there are two big ones. The first is for very long term data retention. When the age of the save sets exceed six months to one year, it is probably no longer economically sensible to store them on deduplicated disk (with the exact timing depending on the underlying change rate of the data). Data this old is best moved to tape for very long term retention. And the PTT features enables NW or NBU to instruct the DL to create a physical volume that matches the contents of the virtual volume, with no additional overhead or load on the storage node or media server.

And, most importantly, the backup application catalog is updated so that the backup application is fully aware of the additional (physical) copy of the volume.

The second big use case is for off-site transport of tape copy. Those environments that do not have a network available for off-site electronic replication of the DL can leverage the PTT feature to create a physical tape for off-site purposes. Again, this copy will be an additional entry in the backup catalog, so the application is aware of the backup data now being in two locations–physical and virtual.

For technical accuracy there are a few other fine points we should recognize:

  1. The DL is using NDMP functionality to achieve the move.
  2. In the case of NetWorker, we are talking about a volume clone, rather than a saveset clone.
  3. NW can leverage the feature with the “nsrndmp_clone” command at the command line.
  4. This works when the DL is being used in VTL personality only (i.e. it does not work with the NAS personality).
  5. It requires NW 7.5 (or NBU 6.5) and DL v1.1 code.
  6. PTT is a separate licensable feature.
  7. You should use the same size virtual media as the physical media that will be the target for the clone operation.

Finally, we should note that there is also an “auto-archive” PTT implementation. For users that employ a backup application other than NetBackup or NetWorker, they will be able to use the DL console to instruct the DL to create a physical tape that has identical contents to a virtual volume. The virtual volume can either be retained, or deleted after a successful archive operation (note that the later is technically referred to as an export, and the former an archive operation). It is important to realize however that the physical volume will not have an entry in the backup media catalog in the case of auto-archive implementations of PTT.

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