Incremental backups actually full

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[ronlleffert]

When I request an incremental backup, I get a full backup file.  Comodo Backup v 3.0.17317.130.  Windows 7 Pro 64 bit.  File is labelled as incremental.  Incremental option is selected.  No error messages.

[Guillermo391]

I think what you see is the full, with the files that had changed in the incremental, kinda like a snapshot. I mean it opens both the incremental and the full..

Lets wait for someoneelse to confirm or deny my hhipotesis.

[ronlleffert]

Sorry, I should have mentioned that I have a full and an incremental backup in the same directory, but they are the same size and have the same files with the same dates and times.  I think what you are saying, is if I do an incremental without having done a full, I will get a full backup labelled as incremental.

[panic]

I think what you are saying, is if I do an incremental without having done a full, I will get a full backup labelled as incremental.

Correct.

Think of it this way, an incremental backup contains the data that has changed between when the incremental job is run and the previous time the incremental job was run. In other words, an incremental job contains the difference between "then" and "now".

When I initially set up and run an incremental backup job, it will back up all files. It does this to establish the "then". The second time it is run, it will compare the status of the "then" files to the state of the files as they currently exist and backup any new files and any files that have been modified since the previous incremental (these are the "now" files).

Hope this helps,
Ewen :-)

[ronlleffert]

Thanks for the clarification, but I did a full backup first.  Then I did an incremental backup on the same directory, and it still backed up all of the files, even though nothing had changed.  I did this because I had previously backed up my user directory, then set up a schedule to do daily incremental backups.  But I kept getting full backups every day.  Then I started experimenting with a much smaller backup (1 directory of 35Kb), and it did the same thing.  The incremental should have been empty, since nothing was changed.  I have tried uninstalling the program, cleaning the registry, then reloading the program.  Same results.  What am I missing?

[sbudaj]

I have a similar problem except it is more sporadic.

I have CB set to do a full backup weekly and incremental backups daily.

Sometimes, the incremental backups are really "full" backups even though they have "inc" in the file name and even though I have a full backup in the same folder. I can't seem to be able to predict when this will happen.

[panic]

Thanks for the clarification, but I did a full backup first.  Then I did an incremental backup on the same directory, and it still backed up all of the files, even though nothing had changed. 

You did a full backup - lets call this "Backup job A", and you've set up an incremental job to backup the same file list as Backup job A - let's call this "Backup job B".

There is no relationship between backup jobs A and B. They are totally separate tasks.

When Backup job A runs, it dies what it is supposed to do - a full backup of the specified files/folders.

When Backup job B is run for the first time, it will back up all files you specified when Backup job B was created. As that job (Backup job B) has not backed up anything yet, there is nothing to increment from, so it backs up all specified files/folders. The second time it runs, it uses the list of files that it did backup when first run as a sort of a baseline to determine what files/folders have changed since it was first run.

Each backup job is independant of all other backup jobs.

Hope this helps,
Ewen :-)

[sbudaj]

"Each backup job is independant of all other backup jobs."

So why not just set a job to do only incremental backups. The first one, under your scenario, will be a "full" backup and the following will be true incremental. Periodically you could delete the full backup and it would start the cycle over again?

[panic]

So why not just set a job to do only incremental backups. The first one, under your scenario, will be a "full" backup and the following will be true incremental.

That's actually the correct way to do it.

[Emanuel Sescu]

So why not just set a job to do only incremental backups.

I agree
You can even store the full backup and all incrementals in same backup file to avoid having so many files.

Thanks

[ronlleffert]

Thanks.  Your comments have clarified the issue for me.  I did a second incremental backup last night, using the same file name, and sure enough, I could see new files, changed files, deleted files and unchanged files in the backup list.  What surprised me was that to back up my user (225 Gbytes) took almost 3 hours, even for the incremental.  I was amazed at how many files change, even though I hadn't consciously changed anything (lots of system and internet file changes).  Apparently, it takes some time to just check the files before copying them.  Lesson learned  Be judicious about what you really need to back up, if time is an issue.

Thanks again for you great comments.  I've learned a lot about backups.

[Eric-Odessit]

The manual says that you have to create a full backup prior to running incremental.  But, from what you are saying, you actually don't need to do that, since the 1st incremental backup will in fact be the 1st full backup necessary.  Is there an error in the manual?
In light of that, what is the difference between the incremental backup and the differential backup?
Thanks,
Eric.

[panic]

The manual says that you have to create a full backup prior to running incremental.  But, from what you are saying, you actually don't need to do that, since the 1st incremental backup will in fact be the 1st full backup necessary.  Is there an error in the manual?

Probably. What it should say it we should setup an incremental job and the first time it is run it will actually do a full backup, but thereafter it will only do incrementals based against what it backed up the first time it ran and did a full backup.

In light of that, what is the difference between the incremental backup and the differential backup?

An incremental backup archives files that have changed since the last incremental was run. A differential archives files that have changed since the last full backup of those files was run.

Imagine we have a folder that contains three files - A, B and C. If we setup an incremental job, the first time it is run it will backup A, B and C. If we then modify B, the next time the incremental job is run it will only backup B. If we then modify C and run the incremental job again, it will only backup C.

Using the same three files, if we setup a differential backup it will initially backup A, B and C. If we then modify B, the next time the differential job is run it will only backup B. If we then modify C, the next time the differential job is run it will backup B and C, as they have been modified since the last full backup.

The advantage of a differential is faster restores, as all modified files are in a single location. With differentials, they are stored in multiple locations. The disadvantage is that they are larger and they take more time.

Hope this helps,
Ewen :-)
 

[Eric-Odessit]

An incremental backup archives files that have changed since the last incremental was run. A differential archives files that have changed since the last full backup of those files was run.

So, from this explanation it almost seems that an incremental backup is a combination of a full backup and a differential backup after that.  Then the subsequent differential backups will compare the files to the original full backup, while the incremental backups will compare the files to the last backup.  Is this correct understanding?
In light of that I don't quite understand the issue with single location vs. multiple locations.  Isn't it up to the user to set up the location?
Thanks,
Eric.

[sbudaj]

I agree
You can even store the full backup and all incrementals in same backup file to avoid having so many files.

Thanks

How is this done?

Thanks.

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