Backup Exec Rotation Schema Configuration Question

Greetings All:
I'm running Backup Exec 10.d on a 2000 Server with a External LTO3 drive.  We have opted to do full backups for each business day (Mon-Fri).  This comes out to about 112 - 115Gb of data a night to backup on 5 different tapes - one for each day of the week.   With a LTO3's native format this equates to at least 3 backups of a business day's data on a tape over 3 weeks. After that there is like 85 - 90Gb of space left on the tape - not enough for a full backup.  My desired state is a backup scheme to where the tapes will append the 3 versions of that tapes backup day and then overwrite the tape so I am always assured of 3 weeks worth of backup protection.

My problem?  Trying to get the correct retention scheme in my media set's properties.  I've tried various combinations with little success.  In that I can certainly fill the tape with my three weeks worth of data, but the tapes never become over-writable and append-able after they are full.  Now up until Backup Exec I could have sworn that I was an intelligent administrator.  :-)

Could I impose upon all of you who know more than I for some assistance with this?  My dyslexia has me thinking that I need to set my append period for 15 day's (for the 3 full backups I can get on a tape) and an overwrite protection for six day's.  

Your thoughts and comments are greatly appreciated.
Ken CarpenterAsked:
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Overwriting in Backup Exec terminology is starting a backup set at the beginning of the tape. That means that any other backup on that tape will be unusable. So you cannot have it overwrite the first - oldest - backup on the tape, without also destroying the other two backups on that tape.

With your approach you would also have to create two different jobs. One for the two weeks where you were going to append - this job would need to be defined to Append.
For the week where you overwrite, you would need a different job. This job would be defined to Overwrite.

To be honest, you may have to go back to the drawing board and plan your backup scheme differently.
Ken CarpenterAuthor Commented:
Ok, let me add to my original question:  What if I just kept the append period for 15 day's and set the overwrite protection to 0.  Wouldn't this solve my problem?  I mean the tape is in append mode for the 3 weeks it can perform backups against.  And while it's appending its not overwriting.  Then after the 3 backups it will overwrite the oldest backup, then the next oldest, then the last oldest.  Then the process starts all over again.  Hmmmmmmmmmmmmmm..
Ken CarpenterAuthor Commented:
Greetnigs honmapog:

>> To be honest, you may have to go back to the drawing board and plan your backup scheme differently.

Wouldn't be the first time.. :-)  Thank you for your input.  What if I go from a 1x rotation to a 3x?  Set one is used until full,  then switch to set 2.  When set 2 becomes full switch to set 3.  This way even though one set of tapes get's  overwritten there is still a 2 x series of backups that can be queried.  
If I have understood you correctly, you would need 15 instead of 5 tapes. But it would work.
You would still have the administrative complexity of creating and managing two different jobs though. (one to append, one to overwrite).

If you're policy doesn't require offsite or fireproof storage you could put the Monday, Tuesday & Wednesday backups on the same tape, then swap the tape and put Thursday, Friday on the next tape. And have 3 week rotation that way.
And if you had a robotic library you could use this last approach and have jobs append until the tape is completely full. Then the robot would automatically load another tape, overwrite it and start at the beginning of the new tape.
Apologies - I was wrong about the two different jobs. As long as you defined the job with the "Append, overwrite if no appendable media is available", you don't need to create different jobs for Append & Overwrite.
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