[Sirtel]

I don't recommend using an active calibre library on a flash drive. I've tried it and found it very slow and prone to numerous errors.

Also, keep in mind that a calibre library is meant to be used on one device only. So pick a laptop for using Calibre and stick to it. If you intend to use Calibre on several laptops with the same library, you'll end up corrupting your library.

As for backing up, at first just copy and paste your entire library folder to an external drive. Not a flash drive, a proper external drive. Next time you want to update your backup, install FreeFileSync on your laptop with the external drive connected and run the sync in the mirror mode - the original library on the left and the backup library on the right. Remember, the mirror mode, not two-way! It's very important.

Forget any servers or networks. Calibre is not meant to be used with those either.