Today’s Question: Some time ago I was told to always quit Lightroom Classic before doing a full backup. But I don’t remember where or why. So, is it OK to run a full backup while Lightroom Classic is open, or should it be shut down first?
Tim’s Quick Answer: I consider it perfectly safe to run a backup while using other software, including Lightroom Classic. However, I do recommend minimizing the use of software (including Lightroom Classic) that could be making changes while a backup is running.
More Detail: I’ve never seen any indication that running a backup while other software is making changes to files that are being backed up will create any problems at all. There will likely be some degree of performance degradation, but that isn’t generally a significant concern.
If there are changes being made while the backup is running, there is a chance that the backup won’t be completely up to date when it completes. But simply running the backup job again later will resolve that issue.
In the case of Lightroom Classic in particular there is a risk that the catalog may be updated during a backup, or that images (or XMP sidecar files for raw captures) may be updated in the background during a backup. These don’t present any real concern of corruption of files or of the backup.
So, I prefer to keep my computer idle without any other applications running when performing a backup, but it is not critical to take this approach.
Note, by the way, that there have been numerous times when I have needed to work while backing up a hard drive with GoodSync (http://timgrey.me/greybackup), and I most certainly continue working even while my cloud-based backup is being updated by Backblaze (https://timgrey.me/onlinebackup).