[mattzito]

Well, shared filesystems are kind of a mess. If they're some sort of clustered block filesystem, there's all kinds of weird performance edge cases and split-brain potential problems.

If you're using NFS or some sort of centralized filesever, you're going to bump into UNIX performance limitations around things like opendir() with lots of files in a single directory. Not to mention, trying to get any kind of atomicity around NFS is a huge pain - look at maildir as an example of a working model for a much simpler situation, email.

Sure, of course, in the early days you won't run into these issues, bceause you won't have enough objects. But once you start getting into a few hundred thousand files, you'll need to start hashing into subdirs, and deal with all the issues above depending on your tech.