Differential backup suddenly growing to almost full size

[mythos]

My most recent full backup of the C partition is 95Gb (with default compression). I do a daily differential backup which is usually less than 20Gb. On windows 7 I could use the same full backup for months without the differential ever growing beyond that.

On windows 10 however I often see the differential backup growing to almost the size of the full backup in a single day. This time it was 7-10Gb for 7 days and yesterday it suddenly grew to 65Gb. I might have updated some application but that was a couple of 100MB, windows was not updated and I didn't do anything beyond office work on the pc that day. This isn't the first time it has happened either. It seems to happen every few days after the full backup. And of course once it grows it stays that size which forces me to redo a full backup and start over.

Does anyone have some idea why this is happening?

[OldNavyGuy]

You may be confusing Differential backups with Incremental backups.

Excerpts from the IFW User's Guide (pages 235 - 237)...

Incremental -

Incremental backups include only data that has changed since the most recent
backup was performed—whether the most recent backup was a full backup or a
previous incremental backup

Differential -

Differential backups include only data that has changed since the most recent full
backup was performed

By its nature, the size of a differential backup grows over time. If you wait long
enough between full backups, your differential backup could become almost as
large as a full backup, and take almost as much time to create.

[TeraByte Support]

what version are you using? If 3.58, you need to upgrade because FAT32 would be raw. Otherwise, you can use tbiview to see what changed under the view option to show lba/changed files.

[mythos]

Hi, thanks for helping.
The list of changed files in the 65GB differential is 320.000 lines and includes most of my C: partition. Even things that I haven't touched in years like photos. Obviously I haven't changed any of that so why does TB suddenly think that I have and backs them up?

On the previous day the differential backup was 7GB and the list was 95.000 lines. I looked at those files and they seem like logical things that could have changed (like winsxs fles etc).

What could have triggered this huge increase? TB suddenly thinks 10 year old files have changed.

[TeraByte Support]

They are in a different location - such as a defrag or something like that.

[mythos]

Do you know of anything that could have caused this? Of course I don't run defrag on an SSD and widows doesn't either. There's no scheduled task that could have caused this.
If this is something that windows 10 does regularly then it should be something well known. I can't be the only one with this issue.

[TeraByte Support]

Create a new base image.

[mythos]

I have done this several times. This is not a on-off issue. I keep creating new base images and after a few days the same thing happens.

[TeraByte Support]

Seems like it would be something like some type of defrag running if the changed files are files that haven't changed. Is your drive ssd or traditional spinning platter? Do you use the speed up option or just plain method?

[mythos]

It's an SSD and as I said I don't defragment it or have any scheduled defrag task for any drive. What do you mean by the speedup option?