Knowledgebase: Backup Strategies
Backup spanning over several media
Posted by Sven Koester, Last modified by Andre Kuehnemund on 22 July 2011 12:40

Most people prefer to associate the backup media with cycles in order to be able to remove one cycle's (e.g. one week's) worth of media and store them in a safe place. When using virtual jukeboxes on hard disks, this does not always make sense, as one cannot "take away" a part of the hard disk. It can even prove to be a disadvantage, since there will always be space left on the last tape of a backup cycle that remains unused.

A scenario where this strategy does make sense is when there are no clear backup cycles, e.g when most backups are started manually (when the laptop to save is present). This method attempts to "pack" data. To achieve this, you have to set "Append to tape" instead of "Use new media" in all backup plans and choose the number of backup cycles to keep.

How does this work?

At the end of the first backup cycle, the last medium will not be closed before starting a new cycle, but data will be appended until the tape is full. There is one drawback to this strategy: the last medium will be recycled one week later than the rest of the media belonging to the same cycle. This is because will hold data of the current cycle, too. The required amount of media is twice the amount required for one whole backup cycle plus one additional medium. Therefore, this strategy can only be used provided there is at least one medium more than required to hold the data of two cycles, since there will always be one medium that contains both an older and a newer cycle and will therefore be recycled one cycle later that desired.

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Comments (2)
Max Gibson
25 May 2016 0:30
Is it possible to create " tape set archives " of very large folders ( FCPX Library ) on external single tape tape-drives ?

I need to span a few Media folders and some FCPX Libraries that are much larger than single LTO4 tapes currently we are using. Up to this point I have been dividing the folders to subfolders to accommodate the limitations of the LTO4 tapes and archiving the the subfolders painstakingly one at the time. I understand that I'll have to do the mechanical part of the work regardless but I am hoping for an automated spanning the data across the multiple tapes.

MacOSX 10.6.8 - IBM LTO4 External single tape drive - Folders as large as 5TB

I apologize if this has been discussed in knowledge base pages of the website. I wasn't able to find it.

Andre Kuehnemund
01 July 2016 11:21
Hi Mat,

Yes, this would work. P5 would write to the first tape until it is full, then request a new tape. Once the new tape has been mounted, the job would continue.
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