This guy is already @366M objects and growing... halving or quartering the number for file i/os in a large system like this has real, observable and proven benefit. It's definitely not for the meek, but adding another directory (and adding an additional metadata lookup) is not the way to go. When you get to more than a billion objects all requiring 5+ metadata entries that need to get walked on every request, you might see it differently.

No, that's silly. You're not changing the number of I/O operations at all. You're simply moving the location in code where they are done from the kernel's filesystem to the applications's userspace. There's no reason to expect either to be faster by anything other than a constant factor.

Isn't what both of you are describing a filesystem in itself?