[slm]

Well, I've read the advice never to run Calibre and a cloud-sync program like Dropbox or Box at the same time. And despite that advice, I have stored my Calibre library in a dropbox-synced folder on my hard drive for the last fifteen or so years.

All of the files stay physically present on the hard drive. I never modify a file in the library in any fashion except through Calibre but I do retrieve some files form the cloud version for other uses.

So far, fingers-crossed, no issues.

I understand that I have been warned that this is will someday cause a mess, and I believe that warning. In the hope that when that disaster happens I will have a strategy for recovery, I'd really like a technical explanation of what Calibre is doing that might result in the Calibre library becoming messed up and what kind of mess might occur. For example, is the damage likely to be to the database files or is there a chance that some of the ebook files themselves will be corrupted?

(In passing, I should mention that I've always been impressed with Calibre's file handling. It seems to be quite fault-tolerant.)

Many thanks.