• By default, CCC will process up to four folders simultaneously and copy up to eight files simultaneously. This update reduces simultaneous folder handling to two if CCC cannot verify that both the source and destination are Solid State devices. We have also exposed a setting that allows the user to adjust this value manually in Advanced Settings > Performance & Analysis, including an option that configures the task to use the CCC v5 legacy file copier instead of the new file copier.
  
  
• Addressed a case where CCC would abort the backup task, indicating that a subtask had timed out, in cases where the destination was particularly slow to deliver information about a folder that had an exceptionally high file count (e.g. tens of thousands, or millions).
  
  
• Fixed a math issue that was previously causing inflight snapshot or SafetyNet archive removal to not remove enough snapshots or archives in cases where the destination was very full.
  
  
• Fixed a scheduling issue that was causing "When files are modified on the source" tasks to not resume monitoring when the task was back within a user-specified time limit.
  
  
• "Next run date" in the CCC Dashboard now correctly rolls over from "tomorrow" to "today" when the date changes.
  
  
• Addressed a handful of crashers and exceptions.
  
  
• When thinning snapshots, CCC now indicates the name of the snapshot using the user's preferred date format.
  
  
• The "Files evaluated" statistic is now updated appropriately during a Preview run.
  
  
• File and folder name changes that only affect the case of characters in the string are now detected (i.e. when that is the only change to the source file) and applied to the destination.
  
  
• CCC will no longer preserve system-immutable file flags when restoring items to the startup disk. This was leading to the creation of a folder (typically "Users") that couldn't be removed by the Finder.
  
  
• CCC now properly imposes a High Sierra+ requirement for the Remote Macintosh feature.
  
  
• Fixed the tooltip on the Source selector when a Big Sur startup volume is selected. Technically that volume is not mounted, but pointing this out is not really necessary.
  
  
• Added color pickers for the lines on the Dynamic Performance Chart.
  
  
• Improved the handling of moved folders in the Quick Update feature. Technically these don't cause modifications to files, but nonetheless we should apply these changes when the task runs.
  
  
• Fixed an errant case-conflict error that can occur on Case Sensitive APFS destination volumes when a folder name has a non-normalized Unicode character.
  
  
• Corrected the behavior of the "Remove excluded files" setting in the Task Filter window. Folders were only getting removed when explicitly excluded via a custom rule (not when unchecked in the main table), and files that were only implicitly excluded (i.e. via the default filter behavior) were getting removed. While that matched CCC v5 behavior, it was not the more conservative result that we were aiming for.
  
  
• When creating a read-only disk image, CCC now uses sparsebundle as the default format for the intermediate read-write disk image. Big Sur, in particular, seems reluctant to create sparseimage files, especially on NAS volumes.
  
  
• Fixed a timing issue that led to errors when running a "When files are changed on the source" task soon after startup.
  
  
• Addressed an edge case in which a source NAS device may lie about the nature of a symlink (i.e. initially the NAS reports that it is a regular file), leading to errors.
  
  
• Corrected the presentation of the startup disk's custom Snapshot Retention Policy.

More info on Carbon Copy Cloner 6 (including free 30 day trial) at bombich.com.