Calibre does not have any specific library backup/restore tool as such, see
How do I backup calibre?.
Many calibre users use file synch tools to maintain a mirror copy of their library folders and if they're sensible their configuration data too. I've seen mention of Free File Synch, Synch Toys, rsynch, and GoodSync at least. There are lots of relevant threads at MR, do a search for 'backup' in the Calibre forums
Providing Total Commander does not add, change, or delete anything in the folders it is mirroring (i.e. the source folders) then it should be OK. And if it doesn't add any extraneous folders or files to the mirrors (i.e the target folders) you will be able to use them with calibre in the event that the 'production' copies suffer a catastrophe.
BR