I'm designing an iPad/iPhone app using core data. The main focus of the app is sorting and viewing up to 20,000 PDFs They are ~200KB each. Typically its best to not store BLOBS in a DB, but for desktop systems I've typically seen it said that if the blobs are < 1 MB then its fine to use the DB. Any considerations I should take into count? If I store them in the file system can I store them all in one directory and not have performance issues (I won't need to ever get a directory list since I'd store each's path in the DB)? Should I divide them among a handful of directories? If so is there a good rule on # of files per dir?