Backup plan : Disk Based then Tape - Help!

pbgormley used Ask the Experts™
Hi, I'm relatively new to Backup Admin stuff so please bare with me.

We recently bought a little Buffalo TeraStation NAS (1.6TB) and my plan was to do a Full Backup to begin with then a Differential Disk Based Backup every night then at the end of the week, do a Backup of this to a Tape using a DELL PVT 122T (Off-site as part of our DR/BC plan), I'm using Veritas Backup Exec 9.1.
The first Full Backup worked so I set the Differential (Using Modified Time) Backups in motion but a daily differential backup is averaging at 50Gb (approximately 1Gb for Staff) which I know we aren't using in a day. Which is being added on to the backup if you like, At the rate I'm going my NAS will be maxed out in a few weeks & backup to tape is almost out of the question already (PVT Tapes are 160/320Gb)

My question is am I doing this all wrong, is differential the correct method ?

I'm almost 1 week into the process, will it level out, am i worrying to early ?

Thanks in advance
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Most Valuable Expert 2013
How long do you need to retain your backups?  

If your new to backups, you might want to review my article on backups.


I suppose 1 month would be suffice.

That looks like a really good article.
Top Expert 2014
You've probably set the full backup to use archive bit and the differential to use modified time, that way it doesn't track the modified time and there's as much backed up in the differential as there is in the full. See 
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Top Expert 2006

Where i work, we use a backup to disk and then once a week to tape scenario. In addition, we keep two weeks of backups on disk.

IT works, because the data is more easily accessible for restoring, and archives for posterity.

Good Luck,


As you're using backup to disk, I would suggest to use incremental instead of differential. Bit more of a hassle to restore, but will save you significant volume.
In regards with you specific issue, might be interesting to enble detailled login to have a look to what has been during the Differential backup. the volume volume might come few files that you could handle separatly.

Quick note about your backup plan, you're sendind your data out once a week, meaning  that if your lose your facility (or have serious damage on your backup system as well as production) you might lose up to 6 days of work. Would that be sufficient for your needs ?

Top Expert 2014

I don't see how "How long do you need to retain your backups?" can have any effect on the size of differentials. Could you explain what you did to solve the problem please.

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