Question

Question says it all.

Is there a limit of files a folder can have?
if not, will there be implications if a folder holds too many files? if so, how many is too many?

Answer 1

Edit:

Please see How many files in a directory is too many? — note dir_index, claims an upper-bound on files in directory. Then see Ext3 – handling large number of files in a directory and the bad performance when not using dir_index 🙂

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Wiki: EXT3 seems to indicate it’s “unlimited”. One disadvantage of “too many” files is with programs that aren’t designed to work with with so many files — for instance a GUI that “locks up” while trying to load the directory contents.

Since the underlying storage is a B-tree variant, looking up a specific file name is generally fast. (This also covers issues with readdir.)

Happy coding.

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For what it’s worth, proxies (like Squid), use multi-level directory structures by default. Then again, the amount of expected cache files is rather large compared to the number of say, documents, a normal user may have 🙂