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Why do we need all Diff Backups instead of the last one

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Hi, I use backups since long time and I understud in regards of the Diff Backup, that all Diff-Backups containing all files since the initial Backup. That means to me, when I have the initial Partition Backup and the last Diff-Backup, I can restore a crashed System with the date of the last Diff Backup.
Now I have a crashed PC and the owner has, in regards of Disc space, several Diff Backups deleted, but he has the initial Backup and last Diff Backup. But when I try to run a restore, Acronis (2010 or 2011) tells me that some of the backups are missing and the restore failes. I must now restore the system to the date of the initial Backup which is long time ago.
What is the mistake in my thinking in terms of the Diff-Backup? I thought keeping every Backup is only necessary with incremental Backups.
Thanks and regards,
Bernd

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If you are sure the backups are differential based on the full backup that you have, you should only need the last differential backup and the full it was based upon.

I would suggest that you place (Move/Copy) both the full and the last/latest differential backup files into a folder of their own, then boot to your Acronis Rescue Media (bootable CD/DVD/USB drive) and perform a validation on the backup files. If the validation succeeds, perform the restore/recovery from the bootable Rescue Media. If the validation fails, then you either do not have differential based backup files (and are missing one or more of the incremental backup files), the differential file does not belong to the full backup, or the differential backup file is corrupt.

For those TI versions, my experience has been that the validation will fail every time but the restoration will succeed and must be done from the TI Bootable Recovery CD.

The problem of failing validation when deleting intermediary differential(s) seems to be fixed with 2013 (I just tried).

Hi all of you,
thanks for your infos and explanations. The good thing is, I don't have to rebuild my knowledge about the Backup methods!
New for me is the information that the Backup with full and a single Diff-Backup is functioning only when I boot from a CD (or also with F11 ?). I tried my Backup under Windows+Acronis and that was my problem.