Macrium Backup File Size  

Hello,To backup my windows system I use Macrium reflect (free edition), every 4 - 5 days. One is a full image backup and 4 - 5 days later a differential backup and so on.The system uses 31.8 to 32.2 GB on the disk (no restore point).Usually a full image backup is ~20.6 GB and a differential is 2.8 - 3.0 GB.The last full backup image (four days ago) was 21.3 GB, no updates or new programs installed.
Today made a differential backup, its size 9.7 GB !(Deleted it and made another, same size 9.7 GB).Macrium reflect not changed, and nothing changed in the system. (Right now 32.0 GB)Macrium reflect version is 7.2.4744 and system is win 10 1809 x64.Any explanations ?Answers will be appreciatedThanksMotim
System = win 10 1809 x64, 17763.1075

You've probably had a recent Windows update, so a lot has changed. If not, open up both images with Reflect and compare.

Motim said:

...Usually ...a differential is 2.8 - 3.0 GB.... Today made a differential backup, its size 9.7 GB ! ....Any explanations ?

Is the drive being imaged an HDD rather thsn an SSD? If so, then one possible explanation is that between the Full image and the Differential the drive had been de-fragmented, either run manually or by the scheduled optimisation.

The reason this can increase the size of a Differential is that moving files around is just as much of a change to the sector contents as would be updating the files. Any change to the contents of the sectors is a 'difference' that has to be recorded in the Differential, even if the file contents haven't actually changed. This effect is even more noticeable if you make Incrementals, which normally would be smaller than a differential.

For that reason I turn off the scheduled optimisation on all my HDD machines. I will only run optimisation if it's needed just before making the next Full backup.

Bree said:

Is the drive being imaged an HDD rather thsn an SSD? If so, then one possible explanation is that between the Full image and the Differential the drive had been de-fragmented, either run manually or by the scheduled optimisation.
For that reason I turn off the scheduled optimisation on all my HDD machines. I will only run optimisation if it's needed just before making the next Full backup.

Hello,
Thanks for the answer and detailed explanation. This will be a lesson for me. The disk is HDD, and I checked, there was a defrag this morning, I did not noticed that.
So again, thanks a lot.
Motim

Motim said:

The disk is HDD, and I checked, there was a defrag this morning...

That would be it then. Remember, a Macrium image isn't just a record of all the used sectors, it preserves the sector layout too.