To add to the conversation, my system backs up to a second identical raid each night, which then backs up to another raid. Once a week that is synced to an offsite Synology. All of these backups employ a system where all replaced files are archived for 2 weeks, which means I can easily go back and find multiple versions of a catalog file if something happens.
Yeah, I know a little over the top, but the only sure backup system is redundant copies of data. I gave up on raid 5’s a long time ago, since they really aren’t designed for backup.
All that yakking just to mention that I never have Lightroom backup it’s library file.