User-389939489 posted
NTFS supports it but, when you get past the thousand items in a folder, things start slowing down dramatically: this is because the item lookup is a linear search across the items list.
So, in order to keep those images on the file system, you'd need a less flat hierarchy. In your case, that might look like:
-- root
-- -- group_1 (ids from 1 to 1000)
-- -- -- user_1
-- -- -- user_2
-- -- -- ...
-- -- -- user_1000
-- -- group_2 (ids from 1001 to 2000)
etc.
That said, and from what I can understand of your requirements: IMO yours is the perfect case for storing those images into a database table instead. It's technically trivial, simpler than storing on the file system; OTOH, from a conceptual standpoint, there
seems to be no point in seeing those images out of the context of a user profile.
HTH,
-LV