directory size optimization
About
The question of directory size optimization arises when designing code-managed file repositories (i.e. a potentially quite large collection of files that is generally not exposed directly to any users, and which is organized and maintained algorithmically).
The question seems to boil down to the ideal number of files to permit in a single folder before dividing that folder's files into multiple subfolders. The best answer depends heavily substantially on the filesystem being used, and thus is best determined by running optimization tests with invented data, trying a variety of different numbers and slowly homing in on what is fastest.
It's generally safe to say, however, that the ideal number will probably be somewhere between 1,000 and 10,000, where the number of files being stored exceeds whatever number is chosen. For smaller numbers of files, the question may be largely irrelevant as any gains in speed will be small.