Antivirus software may interfere with a backup

This article is for an older version of CCC. You can find the latest version here.
Product: 
ccc3

Some antivirus applications may prevent Carbon Copy Cloner from reading certain files, mounting or unmounting disk image files, or, in general, degrade the performance of your backup. In some cases, antivirus applications can even affect the modification date of files that CCC has copied, which will cause CCC to recopy those files every time as if they have substantively changed. In another case, we have seen such software create massive cache files on the startup disk during a backup, so much so that the startup disk became full. We recommend that you temporarily disable security software installed on your Mac (e.g. for the duration of your backup task) if problems such as these arise.

If you experience problems copying files and note that error messages such as "Operation not permitted" are reported in relation to the problem:

  1. Determine whether the files in question are being quarantined by your antivirus software. Perform a system scan with your antivirus software and address any issues that are reported. Please refer to the Help documentation associated with your antivirus product for more information.
  2. If the problem persists, try running your backup task with the antivirus software temporarily disabled.

If these steps do not address the issue, or if you do not have antivirus software installed, please start a discussion in the Discussions area of the Help Desk.

"CCC copies every file, every time!"

Some anti virus applications tamper with file modification dates. After CCC has copied a file to the destination, the very last thing that it does is to set the file's modification date to the modification date of the source file. This filesystem activity prompts the AV software to scan the file, which is generally OK (albeit with a performance hit to the backup task). Reading a file is not sufficient to change the file's modification date, so well-written AV applications should cause no harm by scanning the files that CCC copies. When an AV application "touches" the file, however, or otherwise makes changes to the file, the modification date will be updated to the current date.

CCC's default settings instruct it to copy a file whenever the size or modification date of the file is different on the source and destination. This includes the case where the modification date of the file on the destination is newer. If you cannot resolve the modification date tampering of your AV software, you can configure CCC to only copy files that are newer on the source:

  1. Choose your source and destination in CCC's main window
  2. Click the "Customize these settings" button
  3. Check the "Don't modify files that are newer on the destination" box
  4. Save your settings and proceed with your backup task, or click the "Schedule this task" button to create a new scheduled task

Problem reports related to antivirus software