Newbie Question: why are incremental backups so large?
Hello all,
I am a new user of True Image and would like to understand why incremental backups pick up so many unchanged (by me) files. I suspect that many new users have the same question. If there is a knowledgebase article or similar resource, could someone please provide a link to it.
Here is what I did:
- Ran a full backup (on Windows 10) of a 8.5GB folder to an external hard drive. A 7.7GB backup was created. All good so far.
- The next day, updated the folder to create small test file (less than 50KB) and modified an existing small file (also less than 50KB). No other files in the folder were added or changed. When the incremental backup ran for the folder, a 2.9GB incremental file was created. This contained copies of many unchanged files. I expected that it would contain only copies the new and modified files.
How come the incremental backup picked up many more than the 2 files I expected?
Thanks for your help and apologies in advance if this is a dumb question.
Chris


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Um...
I don't quite understand what you did. You said you created a full backup, and then created an incremental. I think you may have created two independent backups.
A full backup scheme is just that: a full backup. If you run it again, you'll get a full backup.
An incremental backup scheme creates a full backup the first time you run it. The second, third, etc. times it runs, it creates an incremental backup.
If I guessed correctly, the next time you run your incremental job it will create a much smaller file.
I suggest you take a look at the actual backup archives. The naming isn't straightforward, but the parts you need are pretty obvious. You'll see the name of the backup job and whether or not it is a full or incremental backup. The very first backup made by an incremental backup job will actually have "full" in its name. The second will have "inc" in its name.
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Hello Steve,
Thanks for your reply.
The 'folder' that I am backing up is actually 2 folders: c:\users\<myusername>\appdata and a personal documents folder, on the c: drive, outside the c:\users\<myusername> folder.
- From a backup perspective, does it make any difference if my source folder is inside/outside the c:\users\<myusername> folder?
I assume that Windows Maintenance would have run between my initial full backup and the first incremental.
- Can Windows Maintenance cause a file to be picked up in an incremental backup?
Thanks for the info about 'seeing through' the incremental to the full backup. This makes it difficult to understand which files were picked up in an incremental backup.
- Is there an aconis log somewhere that lists the files included in a backup?
Thanks
Chris
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Hello Jerry,
Thanks for your reply.
I have set up a backup that runs daily. The first backup was a full backup, the second was an incremental backup then I changed the backup scheme to take differential backups rather then incrementals.
I have seen that the full backup was larger and the incrementals/differentials were smaller. I am trying to understand why the differentials are much bigger than I expected, given that I have made minimal changes to the files in the source folder.
Regards, and thanks for your help
Chris
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Chris, you said that c:\users\<myusername>\appdata was one of the folders in your backup. This folder contains data from just about everything running. So while you may have only touched a couple files explicitly, your system was messing with the appdata folder. Hard to say how many files were touched there.
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Ditto to Bruno's comments about having the AppData folder as one of your source data folders - there is a whole lot of activity touching those folders.
Another issue to be aware of even with just having c:\users\<myusername> in your source selection is that this can include such as OneDrive, Dropbox type folders, plus can include symbolic links to files stored in the cloud for such services, which can give errors.
There is no log showing which files have been captured when doing any of the backups other than a high level list of the source data from your task configuration.
Download a copy of the MVP Log Viewer tool from the Community Tools link and use this to look at the log file contents.
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In reply to Hello Jerry,… by truwrikodrorow…

Have you looked in the program help? There's a very nice explanation of the difference between full, incremental, and differential schemes.
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I have removed c:\users\<myusername>\appdata from my backup and files sizes are now much smaller.
I am learning about Windows system files as I learn about Acronis and backups :-).
Thanks to everyone for your help
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Chris, glad that you are making progress with understanding what you are backing up and what to exclude etc.
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https://kb.acronis.com/content/2712
2712: Acronis Backup Software Creates Large Incremental or Differential Backup Archives
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