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Question on Backup Methods differential and incremental

Created: 20 Sep 2011 • Updated: 21 Sep 2011 | 8 comments
This issue has been solved. See solution.

Hello,

I have a question to above mentioned backup methods.
Running Backup Exec 12.5 for Windows Servers Backup-to-Disk.

Choose for my backup job differential or incremental method.
When the job runs the first time without having a full backup does it do automatically do a fullbackup ?

Kind regards,
Roland

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pkh's picture

No.  You would have to do a full backup to establish a baseline before you do either an incremental or a differential backup.  Otherwise, your unmodified files would not be backed up.

RahulG's picture

You should ideally run a full backup , but incase if you are backing up for the 1st time and you run a incremental backup it would be like a full backup .

pkh's picture

If you are using the archive bit method and there are files without the archive bit on, the incremental backup will not back them up.  

Roland Schmid's picture

If you are using the archive bit method and there are files without the archive bit on, the incremental backup will not back them up.

the files how they get there archiv bit ?
a differential backup would backup them (the files without archiv bit) ?

 

 

pkh's picture

The archive bit is set when a file is modified.  An incremental or differential backup will not backup files that do have archive bit on.  That is why you need to do a full backup to backup all your files, regardless of whether their archive bit is on or off.

SOLUTION
RahulG's picture

When you create or modify  a file there is a archive bit flag set on the file , when you run a full backup the archvie bt gets reset (which means the file is backed up ). Next time when you modify the file again the archvie bit flag is set again so when you run the incremental backup it knows the file needs to be backed up .

So the incremental backup will backup all the files which were created and modified after the last full backup, so if the full backup is not taken then it will backup all the file which as the archvie bit set on it (all the new files in your case no backup was taken so all the files should have the archvie bit set on it , so it should backup all the files )

When you run the incremental backup it would backup all the files which as the archvie bit set on it and then reset the archvie bit once the file is backed up . Next time you run a incremental backup it would backup any new files created and the old files which are modified .

On the other had differential backup does not reset the archive bit , it justs backups up all the file with the archive bit. so next time you run a differential backup same set of files which are backedup gets backedup again and it also includes the new files created .and all the modified files .