Full backup wwas named My partitions*.tlb but first differential is named PartDiff*.tlb

All backups require a full.  The full is the first backup in any backup plan.  Apparently, you have a scheme that includes differentials as well.  Differentials are the difference between the original full and what has changed since then.  Each differential will build ONLY upon what is not in the full and each differential is completely independent of any other backup file, other than the original full.  The idea behind differentials is that you save space with differentials, vice, taking a full backup every single time.  

Incremetnals, on the other hand, are 1) based of the original full and 2) also based of each incremental that came before it.  Incrementals have the potential to be smaller than differentials with each change since they only backup the difference since the last incremental.  However, incrementals are more susceptible to corruption or failure (especially over time or when there are many of them) since each incremental is dependent not just upon the original full, but also every inecremental that came before it.  

In short, both incremetnals and differentials can be good, but have their downsides too.  Both save space and time by not requring a full backup each time.  Diffs are more reliable since they only require the original full, but can be bigger because each differential backs up all changes since the last full. On the other hand, incrementals are the most space saving, but can be more susceptible to corruption or failure if they go for a long time or have many incrementals to rely on since they only backup the changes since the last incremental and thus, require all incrementals that came before them, to also be reliable. 

Hope that helps. 

Thank you for the excellent explanation of differential and incremental backups.

What is strange to me is that there is a differential backup without a full backup of the same (root) name. For the full backup, the root name is My Partitions; for the differential backup it is PartDiff.

Please consider a hypothetical case: file foo.bar was created on 2016-12-01. It has not been changed since. So it will be in My_partitions_full_s1_v1.tlb. If PartDiff_diff_b1_s2_v1.tlb is a differential of My_partitions_full_s1_v1.tlb, restoring from PartDiff_diff_b1_s2_v1.tlb should restore it.

But the root names are different. So how can ATI know that PartDiff_diff_b1_s2_v1.tlb is a differential of My_partitions_full_s1_v1.tlb ?

It is my understanding that there can't be a differential without a full. But this is what I think I see in E:\Petra backups.

I find myself thinking that there is a bug somewhere (which I find hard to believe)!

I have only backed up twice to E:\Petra backups. I have never deleted any files from E:

...chris

Hi Chris - any chance you manually moved or deleted some files in Windows Explorer (outside of Acronis) at some point in time.  That's the only way I can see there being a full with one name and a differential with another, where there is no other corresponding full for that diff.  

You're right, you cannot have a diff without a full first - at least not as far as creation goes.  However, if files were ever manually moved, renamed or deleted, that could leave some discrpency.

You could take some screenshots and upload them here for some confirmation of what you're seeing.  Try sorting by date created and by name as one view might make it easier to see what corresponds with what, depending upon how the files are sorted in Windows File Explorer when you're loking at them.

Chris, if you rename the backup task after creating the initial full backup image, then any further differential or incremental backup images you create for the renamed task will take the new name.

See screen shot below where I created a task called 'test1' and created a full backup, then renamed the task to be 'was_test1' and then executed the task again to create the first differential which now has the new name.

Such name changes will be tracked within the Acronis Database.

Steve's explanation fits with what I remember of what I did when I set up the task: I missed naming the task before the full backup, and named it after the full backup.

It is comforting to learn that the change in name will be tracked.

Bobbo: I only used Windows Explorer to view what was in E:\Petra backups. I was careful not to delete or rename.

Thanks to you both.

Chris, if I remember correctly this was a change of behaviour introduced sometime ago for ATIH 2016 to allow for tasks to be renamed and the new names used in the subsequent backup files.

The main thing is that the mystery is solved!

Yes, I feel better now, thanks to you guys!