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How does file level Direct Access Recovery (DAR) work?

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Applies to

  • DATA ONTAP 9.x
  • NDMP Backup/Restore

Answer

Process when file level DAR is used:

File level DAR backup

  1. The backup software requests the file(s) for the backup job
  2. The filer starts the five phases of the backup process. See  NDMP / Dump phases description for more information
  3. The information is stored on the internal database of the backup software for later recovery

File level DAR restore

  1. The filer receives the filename, and the offset map created from the restore
  2. The filer seeks through the tape to locate the directory that the file is contained in. This could span the entire tape or even multiple tapes until the offset is reached
  3. The entire directory structure is read and compared and selected file is located and restored along with the metadata

Depending on the number of files in the directory, position of directory and file on the tape, and the number of tapes needing to be read, this process can take a long time to complete

Additional Information

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