Macrium Reflect question  

I've been told I should be doing backups more often. My last one was 1.5 years ago and was a full disk image backup. I heard that a differential backup could be done that would simply update my original backup. So now I did that after looking up directions on how to do it and following them to the letter. But I'm not sure of the result.

My original backup was about 76GB in size. Now I did a differential backup and now have a separate file that's 29GB in size. I was under the impression that the original would simply be changed, so I'm surprised to have a separate file. If I needed to use my backup to restore my computer in the event of a crash, which of these 2 would I use?

Here's a screenshot of what's on my external drive (click it 3 times to see full size):

Here's how a differential backup works....

You create the original backup - this is a complete backup of the disk.

Some time later (let's say a week later) you create the differential backup. This will create a new file but with only the delta (the changes) since the original full backup was created.

Now let's say that you create another differential 2 weeks after the original full backup. That will again result in a new file with all changes since the original backup.

To restore your system to the time when a differential backup was taken, Macrium Reflect would first restore the full backup and then apply the changes from the differential.

The advantage here is that if you have multiple differential backups, you can go to the point in time where any one of them were taken.

As an example, say on Jan 1 I create a full backup. Every week I create a differential. On Feb 1 I discover that I accidentally deleted an important file on Jan 15 and my latest differential was on Jan 25. The backup on Jan 25 would no longer contain the deleted file, but any of my backups before Jan. 15 would.

Does that help?

Hi,
After 1.5 years maybe just use monthly full images and try to keep at least 2 before you start removing/ replacing for the third but this all depends on how much storage you have as to how many full images you can store.

hsehestedt said:

Here's how a differential backup works....

You create the original backup - this is a complete backup of the disk.

Some time later (let's say a week later) you create the differential backup. This will create a new file but with only the delta (the changes) since the original full backup was created.

Now let's say that you create another differential 2 weeks after the original full backup. That will again result in a new file with all changes since the original backup.

To restore your system to the time when a differential backup was taken, Macrium Reflect would first restore the full backup and then apply the changes from the differential.

The advantage here is that if you have multiple differential backups, you can go to the point in time where any one of them were taken.

As an example, say on Jan 1 I create a full backup. Every week I create a differential. On Feb 1 I discover that I accidentally deleted an important file on Jan 15 and my latest differential was on Jan 25. The backup on Jan 25 would no longer contain the deleted file, but any of my backups before Jan. 15 would.

Does that help?

Yes, it does. Thanks! I was under the impression that the original backup file would be altered and replaced with the newest version rather than ending up with an additional file being created. It does explain why the new differential was smaller.

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Bree said:

hsehestedt has summarised Differential backups well.

I would just like to add that if the disk you are going to make a Full image of is an HDD (not an SDD) then you should avoid defragmenting it if you plan on making Differentials. The reason is that moving the files around on the drive also counts as a 'change' that will be included in the Differential, even though the files themselves are unaltered.

For all my HDD machines I have scheduled optimisation turned off to keep down the size of the differentials. I only defragment an HDD immediately prior to making the next new Full image.

None of the above applies to SSDs, and you should leave the scheduled optimisation turned on. Optimisation on SSDs will not defragment them, just perform a retrim (that has no effect on a Differential inage).

I actually did do a defrag on my computer (I have an HDD) not long ago. Since that qualified as a change on the differential I just made, will it mess things up if I use it with the original backup in the future?

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ThrashZone said:

Hi,
After 1.5 years maybe just use monthly full images and try to keep at least 2 before you start removing/ replacing for the third but this all depends on how much storage you have as to how many full images you can store.

I was told recently that differential backups were smaller and take less time to do because they only backup what is different from the original. This is the first time I've ever tried doing one, and I've never had to use a backup, so I'm kind of a rookie about it.