Just when I was coming to rely on Calibre I discover that large chunks of my library have simply gone missing.

The books show up in the library display with title/author metadata present and an apparent size but there are no formats available - not surprising since the directories pointed to are empty.

These are books which have been successfully imported, converted and uploaded again - they were there and they were fine.

Further inspection suggests that basically all books in mobi format which were present in the library before the beginning of December 2009 have gone. Books added since that date appear untouched. There are books in lit format from before that date but I cannot say whether any lit books have gone. Many prc books are still there, too, so no idea whether any have gone. My guess is that it is only mobi.

As far as I am aware I have never touched the Calibre directory structure - I have only ever downloaded and installed new versions and everything has seemed fine.

OS is Vista 32.

calibre doesn't delete files unless you ask it to. And is certainly doesn't preferentially delete one format and not another. In fact it is designed ina manner such that once a book file is added to the library, it is never touched unless you change metadata, in which case it is copied to the new folder indicated by that metadata.

Hmmm. Nevertheless the files have gone and I've never even looked at the Calibre directories before today. As to working out a way of deleting only mobi files, I wouldn't have a clue, much less a reason to try.

When you say change the metadata, would that include my habit of reversing first/second names in the author name slot as well as sort order after import?

Don't get me wrong, I love Calibre but the fact is that I've only ever used as a simple consumer so I don't think I've done anything clever or even unusual.

Sorry to hear of your problems. Have you tried searching the whole of your disk (not just calibre directories) for *.mobi to see if any of your lost items are somewhere strange?

Sorry to hear of your problems. Have you tried searching the whole of your disk (not just calibre directories) for *.mobi to see if any of your lost items are somewhere strange?

Thanks for the suggestion but I've searched for the specific files and no joy. Nothing is actually lost since I've always kept the original libraries of each format and have already re-imported them. I'm putting it down to a problem in upgrading or a glitch in a previous version.

The only practical consequence is that I've put back the day [year] when I start relying on Calibre alone to keep the library, just in case.

Check your Virus Vault and Log .
I suggest that you exclude the Calibre Librry folder (and All Subs), Further, I heartily recommend you make your Anti Virus ASK what to do when it discovers file x is a bad guy. I have not seen a lot of False Positives, but some would have destroyed any database usability .

Another Database sync killer is disk cache. Some pieces get written (Metadata in this case) and other pieces were in cache, waiting to be written to disk, when something went sour :(
Again, disable write behind caching. It exists to make you think you are done sooner than you are and give back control of your program (while it plays,'catch-up') .

When you click the arrow next to the delete button, there's an option to delete only files of a specific format. That's really the only way I can think that this could have happened.

When you click the arrow next to the delete button, there's an option to delete only files of a specific format. That's really the only way I can think that this could have happened.

Well all the stuff is now reinstalled and I'm going to assume that it happened when I upgraded after a long gap in December. Thanks for listening.

Well all the stuff is now reinstalled and I'm going to assume that it happened when I upgraded after a long gap in December. Thanks for listening.

I wouldn't be so quick to chalk this up to an upgrade glitch. If you do that you may make the same mistake again. In the past I have accidentally moved or deleted things I didn't mean to when I started cleaning items up via the search window.

I'll keep my fingers crossed for you in the hopes that whatever it was that caused this doesn't happen again. :)