Help with understanding the differential scheme

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truwrikodrorowrelupicugojestutroclulachosaswunuhospikigawakijosaswenomaruclojeueclikaspedrubewidebrisubrohutrurifruuagothunugekedrumucisiuobrobrecrupeslapuswosluprothethibakaslechurathikucli
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I have set-up a scheduled backup using the differential scheme.

Please see the attached pdf showing a screenshot of what I set-up.

I expected TIH to make a full backup on day one then differential backups for the next six days. However, when I look at the size of the backup files, it appears to have done a full backup the first day, a differential on the second but a full backup again on the third day (see screen shot).

Have I fundamentally misunderstood how TIH works?

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Mon, 12/06/2010 - 12:26
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truwrikodrorowrelupicugojestutroclulachosaswunuhospikigawakijosaswenomaruclojeueclikaspedrubewidebrisubrohutrurifruuagothunugekedrumucisiuobrobrecrupeslapuswosluprothethibakaslechurathikucli
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Have I fundamentally misunderstood how TIH works?

Probably not. If you have defragged the disk in the meantime TI sees the different arrangement of bits since the defragging and writes them to the image supplementary file. If a disk was heavily fragmented, defragging will reorder most of the disk and the differential file will be large, possibly as large as the original.

Although TI does back up a disk, it remains an imaging program and works in a fundamentally different way from a backup program. A backup program tracks file sizes, flags or dates and backs up files where these have changed. TI looks at the bits on the disk and writes them to an image file.

Mon, 12/06/2010 - 13:52
truwrikodrorowrelupicugojestutroclulachosaswunuhospikigawakijosaswenomaruclojeueclikaspedrubewidebrisubrohutrurifruuagothunugekedrumucisiuobrobrecrupeslapuswosluprothethibakaslechurathikucli
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David Thorpe thanks for the reply. I haven't performed any defrags or any major changes to the data on the disk. So not sure why this has happened. The problem is I don't have enough disk space to cater for TI taking full instead of differential backups on a daily basis.

Mon, 12/06/2010 - 18:50
truwrikodrorowrelupicugojestutroclulachosaswunuhospikigawakijosaswenomaruclojeueclikaspedrubewidebrisubrohutrurifruuagothunugekedrumucisiuobrobrecrupeslapuswosluprothethibakaslechurathikucli
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Strange. I know that win7 can perform defragging in the background as a default after installation. It's all I can think of, you need someone more expert than me.

Mon, 12/06/2010 - 19:23