It's really critical to actually run the LrC catalog from the fastest drive you have. That is usually an internal SSD. The catalog and preview folders are all in one LrC folder. Keep them together.
People are constantly reporting issues with trying to run the LrC folder from OneDrive. That is a big source of catalog corruption.
Thank you. If I click "Always keep on this device", and wait for everything to download, I am now running it from the SSD and not Onedrive, correct?
As an update it did run into problem, but I suspect that this was because I didn't connect my hard drive first, and about 80% of my RAWs were located in that hard drive.
If OneDrive is enabled for the folder on the SSD (is it?) with your Lightroom Classic catalog, then you will still run into problems keeping your catalog files and/or images in a folder that syncs to "the cloud". Your statement that you clicked on "Always keep on this device" indicates that the folder is still synced to the cloud. The fact that the file is on your device does not eliminate the problems caused by OneDrive.
Best (and in my opinion, it is mandatory not optional) to turn off OneDrive for any folder containing Lightroom Classic files or the original images.
Hmm okay, makes sense. However, I have had it synced with Onedrive since the beginning, and never encountered any problems.
Just because you have not had problems yet does not mean you will not have problems in the future. Ken Seals said earlier in this thread: "People are constantly reporting issues with trying to run the LrC folder from OneDrive. That is a big source of catalog corruption." Its very risky, and unnecessarily risky.
I did move LrC to a new PC before, but that time I transferred the folder to a hard drive and then back to its location. However that time it also synced with Onedrive before running it all in LrC. Everything was intact, nothing was lost. The thing is, if my PC fails like last time, atleast OneDrive has all my files updated. Continously moving the updated files to a hard drive is time consuming. Maybe it would be safer to download the files through "allways keep..", then turn off sync before loading up LrC for the first time, and after that I can turn sync back on?
Make backups of your LrC catalog via the built-in LrC backup feature. Store those on OneDrive. Do not store your working catalog in a folder synced with OneDrive.
You can make lots of arguments about how its safe to put your working catalog in a folder synced to OneDrive, I don't buy any of them. And if you don't believe me, you should believe Ken Seals.