Why is incremental larger than full?

I do a weekly full backup and each day thereafter an incremental. For some reason, the Tuesday incremental is larger than the weekly full:

sc.tib 2.82GB (Sunday) full
sc2.tib 3.2KB (Monday)
sc3.tib 2.88GB (Tuesday)

Any ideas how that can happen?

Thanks,
Brett

 

Hello brettr,

Thank you for choosing Acronis Disk Backup Software.

Please see this post for explanations and recommendations.

Thank you.
--
Marat Setdikov

 

The only thing in that post that seems to apply is the System Restore part. I need to have that on unless there is a way to turn it on only during a product install and then turn it off.

 

Hi Brett,

Can you confirm that a disk defragger wasn't run on the source disk prior to Tuesday's incremental?

Regards

 

I rarely run defrag and don't have it scheduled. I'm on Vista. Is there a way to check if defrag has ran?

The end of last week or this weekend, I installed an antivirus program. I has been doing full scans everyday. I've since turned that off. Could it be related to this problem? That wouldn't explain why Monday is so small though.

Thanks,
Brett

 

I can't comment re Vista as I don't use it. Hopefully someone else can pitch in on this. Personally, I doubt that installing an antivirus program will greatly affect the size of any subsequent incremental image. The usual reason for an incremental being as large as the original full image is that the source disk has been defragged in the meantime. Try creating another incremental and see what the size is.

Regards

 

Although I do find Vista Ultimate to be an improvement over XP Pro, Microsoft took a big step backwards with Vista's built-in disk defragmentation. You really have no control over most of it now. I believe it runs every morning at 6:00 am (at least that's what mine is set to do, and I didn't touch it since installation). This could be the cause of your incremental images being larger than the original full backups.

OTOH, I guess this is good for third-party vendors like Raxco, O&O and Diskeeper...