incremental backup jobs perform a full backup

Last post 04-14-2014, 11:29 PM by Trekrod1. 8 replies.
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  • incremental backup jobs perform a full backup
    Posted: 09-26-2012, 9:06 AM

    We have several incremental backup jobs that are running as full backups. By running as a full I mean that they are backing up every file on the system. There is so much data being replicated that the backups are not finishing within the backup window. We did find a Symantec article that states that Symantec Endpoint Protection scans can change the USN change journal on each file causing the backup the think that ever file has changed and backing up everything. Symantec also suggested a regedit, which we tried and did not work. Here is the link to that article:

    I should also say that the job is still listed as Incremental so it's not being converted to a full. Is anyone else experiencing anything similar to this or have any idea what else could be causing these incrementals to run as fulls. Thanks.

  • Re: incremental backup jobs perform a full backup
    Posted: 09-26-2012, 9:59 AM

    Good morning,

    I would recommend reviewing the KB article link below:


  • Re: incremental backup jobs perform a full backup
    Posted: 09-26-2012, 10:37 AM

    Hi JW,

    Thanks for the response. I have tried the Symantec regedit but that does not seem to have resolved the issue. The second solution in this article says "CommVault recommends switching from "Change Journal" to "Classic file scan" with a check to preserve file access time." However in the Commvault documentation it says "For all Windows File System iDataAgents, you can select Use Classic File Scan to scan files; however, it is strongly recommended that you use the change journal."

    Also in the documentation it states: "If you select the Use Change Journal option the file access times will not be preserved and the file is marked as modified." - Does this mean that after a Change Journal scans runs on a full backup all files will be marked as modified? Also wouldn't that mean that the next incremental would see all those files as modified and back them up?

    What are the risks/downsides to switching from Change Journal to Classic file scan?



  • Re: incremental backup jobs perform a full backup
    Posted: 09-28-2012, 8:52 AM

    Hi JamesO,

    Still very likely that symantec is the cause here. Here's how I helped another customer prove AV:

    1. Find a file or directory of files on the file system

    2. Run the following command on that file: fsutil usn readdata <file>

    Example: C:\temp> fsutil usn readdata SIDBEngine.log

    3. Record the USN

    4. Run a scan over the file using your AV product

    5. Check the USN again by using the fsutil function and see if the USN has changed.

    Also, if the files NTFS permissions get changed, that can also cause a USN change as well - had another customer that was running scripts to change permissions etc.

  • Re: incremental backup jobs perform a full backup
    Posted: 09-28-2012, 10:06 AM

    Hi dandre,

    Thanks for the responce. I tried your suggestion which was a good test for determining if Symantec is modifying the USN. Unfortunately after running the test it doesn't look like Symantec is the problem. Granted I only verified this on 2 out of about 500 servers. I wonder if only certain versions of Symantec and/or the OS are affected by this.  Great test though.

  • Re: incremental backup jobs perform a full backup
    Posted: 09-28-2012, 10:18 AM

    Hi James.

    Interesting, must be some other cause then. Are these very large file servers?

    Wondering if the change journal is wrapping due to many changes.

    Also; are you using CommVault SRM at all?

    There is no real down-side to using the classic scan mode - the scan time may take slightly longer depending on the data set.

    Basically instead of checking USN's it will check the timestamp of each file and see if its newer than the timestamp recorded at the end of the filescan phase of the previous backup.

    You could also turn on windows auditing on a directory, to see what may be touching the files and causing a USN shift (other than a backup).

  • Re: incremental backup jobs perform a full backup
    Posted: 09-28-2012, 10:30 AM

    Yes some of these are very large file servers some with thousands of shares on them. I don't think we are using SRM at all. Do you have more information on this change journal wrapping that you are referring to, I would like to look into that? Thanks.

  • Re: incremental backup jobs perform a full backup
    Posted: 01-15-2013, 2:30 PM

    Not sure if your issue is resolved but you may want to review this link.



  • Re: incremental backup jobs perform a full backup
    Posted: 04-14-2014, 11:29 PM

    Here is the current active article URL link:

    Previous ID 6246:

    Incremental or Differential backups are the same size as Full backups

    Supplied by KB Admin

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