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Backup file much smaller than expected

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I have been using Acronis home version for a number of years and versions. My C drive is 500GB and used space generally stays around 35-40%. Used space, as shown in disc properties, has been around 195GB used for a while now. My backups used to reflect this in that the file size for a full disk backup was probably around 120-130GB, if I recall properly. However, my C backups have shrunk to 70-some GB in the past couple of months, and I am wondering why. I think it cooresponds with my upgrading to A2019, though I'm not certain. Perhaps Acronis 2019 has a more highly compressed coding or something? I just want to make sure that it's not skipping something important.

I used WizTree this morning to look at my C drive file allocation. The ~195GB shows there as well, and the only rough correspondence I can make out to the smaller backup is that system info and other files without extensions show as taking up 49% of the used space, about 90GB. I'm way out of my league here, but would appreciate any explanation or clarification.


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Assuming you are running Windows 10 it may have resulted from the removal of the rollback files created when you did the most recent update - the files in the Windows.old folder can take up a lot of space. See information here.


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Philip, in addition to the comments from Ian, we really would need more information to be able to advise you further and understand why your backup size may be shown as smaller.

ATI (all versions) exclude a number of potentially large files / folders by default where those files / folder are automatically recreated by Windows on boot.  It is possible that you were including some of these items previously and they are now excluded.

Look at the Exclusions page settings for your backup task to get a list of what is being excluded then look at the size of that data via Explorer or other utility.
Note: ATI excludes the System Volume Information folders which is where System Protection / Restore point data is stored.  Microsoft disables System Protection in recent Windows 10 versions by default.

Compression would normally expect to achieve around 20% size saving but this depends on the types of files being included.  Some files such as images, videos, music etc are normally already highly compressed so offer minimal saving, whereas documents offer high compression savings.

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Mount the backup as a volume letter. Then launch two instances of wiztree and compare filter sizes of the actual c drive and the mounted backup volume letter. That should clarify the size difference.

My big guess is system volume Information may be rather large and possibly wasn't being excluded, but now is.

Or did you have windows.old from a major Windows 10 upgrade that has finally cleaned up?

If you've made any junction points that could make a difference too. I no longer back up my iTunes appdata as it was growing huge with iTunes phone backups. Instead, i made a junction for that folder to another drive so it appears to the OS as being the same, but since the data is actually elsewhere, it's not in the OS drived backup.


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Thanks to all. I am pressed for time now, but wanted to clarify at least that I am running Windows 7. I had to have it reinstalled in Jan., but it seems to me that the first backup I did afterwards was more of a comparable size, i.e., more like the 20% reduction from disc space mentioned above.

I'll have to look into your other comments. I have no idea how to "mount a volume," much less as a letter, nor what a junction is. I'll have to explore.

Thanks again for your consideration.



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When you have time, right click the .tib and mount it. You then give it a volume letter (like an external USB drive would have) and it will show up in Windows like an attached drive. Then you can compare the folder sizes with your tool and look for any large inconsistencies that might present themselves.