How to avoid hash fails seeding from your Calibre library

If your uploaded torrents (or perhaps, even downloaded ones) keep resetting or not completing the download/upload, then it's quite possible that you're seeding the file(s) from your Calibre library. While this may seem convenient, it can pose problems when Calibre might modify an ebook file, thus causing your torrent seeding to fail. If I can't convince you to maintain a separate, second folder for upload/downloads (especially since most ebook files create such a small footprint), then follow skrtsqrl's advice below, to make sure that the ebooks in your Calibre library seed smoothly.

This is also vital if you plan to upload retail ebooks: if your "retail" upload(s) include a Calibre-inserted bookmark file, it will be deemed "non-retail" and can therefore be trumped by a fully-retail upload by someone else. Changing the setting as explained below will ensure Calibre does not modify your ebooks without your knowledge. - Dio 



There's a change in the latest release of Calibre that is important to note for torrentors. 

Changelog Wrote:

E-book viewer: Add option to not remember position in book when quitting.

This is important because, if you don't set it to this option, or you use an older version of Calibre without this change, any time you view any of your seeding copies of an ebook using Calibre's reader it will insert a bookmark into the file itself, changing the file and making it no longer seedable to 100%. Downloaders will get hashfails from you, although you may not even realize the problem until you do a recheck of your files.

To set it, just open any book with Calibre's reader (ie, click View), click Options (the icon with the gears, should be third from bottom along left side), and uncheck "Remember the current page when quitting" (second from the bottom). This will change it for everything you open from then on.