Backup and Restore with Macrium Reflect  

Reading the past few pages, I thought it would be useful to clarify something. Please click screenshots to pop-out, click again to expand.




Kari

CountMike said:

You have there one backup set, containing one full backup (-00-00), and two differentials or incrementals (-01-01 and -02-02).

Kari said:

You have there one backup set, containing one full backup (-00-00), and two differentials or incrementals (-01-01 and -02-02).

Yes, second one is twice the size of first Differential although there were very few changes to disk. Now it got me wondering if third one will be 3 times size of first or twice the size of second ?
Would incremental have less difference in sizes ? Can't try yet because my MR is free version.

CountMike said:

Yes, second one is twice the size of first Differential although there were very few changes to disk. Now it got me wondering if third one will be 3 times size of first or twice the size of second ?
Would incremental have less difference in sizes ? Can't try yet because my MR is free version.

Probably a build up of temporary files and because these are always changing the size of the differentials will continue to grow. Shows just how much disk activity goes on without us realising it.

kado897 said:

Probably a build up of temporary files and because these are always changing the size of the differentials will continue to grow. Shows just how much disk activity goes on without us realising it.

I do Disk cleanup and UnCleaner as well as Dism every time before making a backup.

CountMike said:

I do Disk cleanup and UnCleaner as well as Dism every time before making a backup.

Don't think that matters. if you think about it unless the very same blocks were cleared both locations are still changed.

A 1 byte change to a block is flagged as needing to be included in diff/incr. 10,000 changes to same block or 1 change is still 1 block change to MR. If the small number of changes is scattered about, the larger the diff/incr. Gotta remember MR doesn't give a hoot about the NTFS when determining what gets included. Not how it works. (I know some files are excluded, like $fillintheblank)

CountMike said:

I do Disk cleanup and UnCleaner as well as Dism every time before making a backup.

Doesn't matter, the smallest change is a difference that has to be included in a differential. It is inevitable that each new differential will be larger than the previous.

Even a defrag without changing a single bit of data counts as a 'change' that has to be backed up (because the file now occupies a different set of sectors). For that reason I have turned off scheduled optimisation on all my machines that have HDDs.

CountMike said:

Yes, second one is twice the size of first Differential although there were very few changes to disk. Now it got me wondering if third one will be 3 times size of first or twice the size of second ?

No, size of your differentials will not grow exponentially. If you want to test it, create a differential, and then immediately when it's finished, another one, and compare the sizes.

A differential saves all changes since the last full image. Seeing that your second differential was created 18 hours after the first one, quite a lot could have been changed (for instance Windows updates, browser history, cookies & cache, and so on).

An incremental image saves changes since last backup, be it full, differential or incremental. Incrementals can be quite small, if previous incrementals exist.

Big difference is what is required to restore an image. Restoring from a differential image, you only need the last full image plus last differential, you can freely delete any images there in between. Restoring from an incremental, you must have the last full image, last differential (if exists), and all incrementals created before the one used for restore. A single missing incremental image makes it impossible to do a restore from an incremental backup set (you can still restore last differential or full image).

I like the incrementals because they are so fast. I use so called Grandfather - Father - Son backup plan: a full backup (Grandfather) is created once a month, a differential (Father) once a week, and an incremental (Son) once a day.

Kari