The sync can be set on various triggers manual or automatic, including the one I use
I use it on my travel Image storage drive It syncs when ever I attach the drive to my Desktop
The default is to attach it to the desktop occasionally ( and certainly when I plan a trip ), this means that the current Lightroom catalog and Image library is on the drive.
When I am away in the hotel I attach the drive to the laptop and Use it to store any work I do when away, (including storing the base image files and the catalogue )
When I arrive home I attach the drive to the desktop and the catalog and images are synced back to the Desktop
( I have room on the drive for the full image library, but if that eventually is not possible there is a Lightroom Virtual Image which allows editing but on a small copy of the original file (Lightroom never touches the original image except when performing an export - so when the drive is re-connected to the desktop the original full size files have the same edits applied automatically as the virtual file )
I bought a perpetual World Backup Day Pro licence for £16.07 as a result of trying this offer. I know I could have waited a year but got a deal via stack social that was too good to miss.
I looked closer at the sync option and I have been playing with it. Very easy to use. I have my main hyper-V virtual hard disk directory and I like to back those up periodically to my external usb drive (from an internal backup folder), and it is a rather manual exercise.
I have used robocopy but I tried automatically syncing the folder (to an internal drive) using Aomei, and I am impressed how well it works.
However, the vhds are large files, and doing it automatically rather thrashes internal target nvme drive, backing up too frequently (I mess around with vms a lot).
So I have now set up a manual task that I run periodically.
I have not done it yet, but I may set up an automatic task for my external backup usb drive (also nvme), using mirror function i.e. usb drive is always in sync with my internal drive backup folder.
So yeah, nice feature. I doubt I will use the backup options (I find them too inflexible), but I can find sync feature useful (despite earlier thinking otherwise) based on your reply which set me thinking.
Actually, I have changed my mind a bit, as I write this.
I will use file and folder backup option of Macrium Reflect Free to backup vhd folder periodically to internal drive backup folder and then automatically sync the image backups (when I plug usb drive in) rather than sync vhds, as this saves a lot of drive space).
I know I could use Aomei to backup vhd folder but yet to test that.
Thanks for giving me ideas.