1.3.3.1 Scenario #1: Full and incremental backups to tape

The figure below shows a diagram of how a tape only system would work.  This scenario’s advantages are :

  • No intermediate disk requirements.  Data goes directly to tape without having to be staged through disk.  This saves on UPSTREAM server disk space.
  • Good for large volumes of data.
  • Only one tape is created per backup cycle (usually weekly).  This saves on tape management.

Fig-3.jpg

When you run your first-time full backup, a new tape is created which holds all the data on your workstation or server (tape 1 in the figure).  The first incremental after a full creates a new tape (tape 2 in the figure).  Subsequent incrementals are appended to the end of the tape volume.

After your first-time full backup, subsequent full volume backups are merge full backups.  In a merge full backup the UPSTREAM client sends up all the files changed since the last incremental as well as a directory listing.  The tape holding the prior full backup is mounted  (tape 1) as well as the tape holding the incremental data (tape 2).

Any files that have not been changed will be copied from tape 1 to tape 2 unless they are in the incremental on tape 2 already.  The files which were in the prior incrementals on tape 2 are recorded as being part of both the full and incremental backups.  The UPSTREAM server software then requests any files which could not be matched. 

Note that if you are using retention periods for tapes, the period begins with the first incremental.  You will want to allow for this in your planning.

The result is a new full backup tape which will be used as the source for the next full backup.


 

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