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Difference between Differential Inc backup and Cumulative Inc backup.

Created: 03 Mar 2014 • Updated: 03 Mar 2014 | 5 comments
This issue has been solved. See solution.

All my backups are archive bit dependant.

Please let me know what is the difference we are backing up in Differential Inc backup and Cumulative Inc backup, if below definitions are correct.

  Please find the attachement.

   

Thanks and regards,

Bharath Achar

Operating Systems:

Comments 5 CommentsJump to latest comment

Mark_Solutions's picture

Differential Incremental backup is the backup of the files that have changed since the last backup (whether full or incremental backup)

Cumulative Incremental is the backup of all files that have changed since the last full backup (so gets bigger each day until the next full is run)

The archive bit only gets reset when you run the full backup when using cumulative incremental backups

Hope this helps

Authorised Symantec Consultant

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RamNagalla's picture

and in your screenshot you have combined the both differential and cumulative backups, and that is not the recommended way when backup are using the archvie bit

see the note from Symantec , page number 109 netbackup admin guide volume 1

Note: Symantec recommends that you do not combine differential incremental
backups and cumulative incremental backups within the same Windows policy
when the incremental backups are based on archive bit.

so that is not the recommended way to taking backup, if you would like to mix both differential and cumulative , go with the backups based on time stamp.

SOLUTION
Mark_Solutions's picture

I missed the screenshot but Nagalla is right on that point - never combine the two in the same policy!

That setup is a very strange one - just have you full once a week and either diff or cumulative on the other days but not that mix

Authorised Symantec Consultant

Don't forget to "Mark as Solution" if someones advice has solved your issue - and please bring back the Thumbs Up!!.

Marianne's picture

I addition to above excellent posts, we also see the following on p. 581 of NBU for Windows Admin Guide 1: Table 15-27 Standard backup types

Cumulative Incremental Backup
Backs up the files that are specified in the backup selections list that changed since the
last full backup. All files are backed up if no previous backup was done. Cumulative
incremental backups occur automatically according to schedule criteria. A complete
restore requires the last full backup and the last cumulative incremental backup.
Do not combine differential incremental backups and cumulative incremental backups
within the same Windows policy when the incremental backups are based on archive bit
(default).
By default, if the time between file creation and a full or a differential incremental backup
is less than 5 minutes, the differential or cumulative incremental backup may yield
unexpected results. The backups are successful, but the additional files are backed up.
See “About incremental backups” on page 583.
 
Differential Incremental Backup
Backs up the files that changed since the last successful incremental (differential or
cumulative) or full backup. All files are backed up if no previous backup was done.
Differential incremental backups occur automatically according to schedule criteria. A
complete restore requires the last full backup, the last cumulative incremental, and all
differential incremental backups that occurred since the last full backup.
By default, if the time between file creation and a full or a differential incremental backup
is less than 5 minutes, the differential or cumulative incremental backup may yield
unexpected results. The backups are successful, but the additional files are backed up.
See “About incremental backups” on page 583.
 
 

So, if you choose backups based on date/time stamp (Windows Client Settings properties), you can use C Inc and D Inc in the same policy.

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