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Incr./Diff. Data Backup: How does ATIH select files to be backed up?

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Dear users,
I'm looking for detailled technical information about how ATIH selects files to be included into an incremental or differential data backup.

There may be several methods, e.g. archive flag, modification time or even a watch-dog process which continuously logs all write accesses to the data files.
Depending on the method used by ATIH maybe that the user has to be aware of some limitations:
- When copying files with xcopy for other reasons it may occur that the archive flag is deleted.
- Some tools for foto or mp3 processing have options to leave modification time unchanged.
- When accessing the data from another OS installation on the computer the watch-dog process is not running. Same occurs for data on external drives if the drive is connected to another computer.
Before using ATIH for data backup and replacing my own zip and xcopy based scripts I want to be sure that I do not run into problems. I hope that the method is not handled as an internal secret of Acronis ;-). But if so, it would be nice to get at least some hints what I should not do .....
Thank you for any help or reference to the information if already existent here.

0 Users found this helpful

Hello Krohnsohn,

Welcome to our Forum, it's nice to have you with us.

Basically the software doesn't analyze the files: it checks the drive sectors that has been changed since the last backup.

Once the backup creation is started, Acronis True Image Home creates a snapshot, then divides it to pieces, and assigns a checksum to each part, Later when it starts to write data to the backup file, it compares the checksum in the snapshot with the checksum of the same parts on the drive. It archives the latest information, and that's how the full is created.

When you're running differential or incremental backup, it created a new snapshot and checks its checksums with the ones of the original or previous (in case of incremental chain) backup. And archives the information regarding what exact sectors were changed.

This ensures us that we have the most recent information correctly archived and protected.

Should you need anything else or have any further questions - feel free to contact us at your earliest convenience, we will be happy to help you!

Thank you.

The above is valid for disk/partition backup. File backup checks only file size and modification time change.

Thanks a lot to Yana and dev-anon. Now I know how to deal with both, data and partition backup.

Yana wrote:
it checks the drive sectors that has been changed since the last backup

This is why, if you use differential or incremental backups, you shouldn't defrag your source drive just before a backup. As the defrag will move files, many sectors will change even if the data did not actually change, so the differential or incremental backup will end up almost the same size as a full backup. That result has confused many ATIH users.

And tuttle's response is exactly why I have asked, time and time again, for the Acronis scheduling route to be written to accomodate that of the defrag utiilty that comes with Windows (7 in my case).

I just made a more descriptive post here:
http://forum.acronis.com/forum/29125#comment-90601