Huge number of files in a directory

["Fábio Jr."]

Hello,

I serve static content with an Apache server, and store the files in a 
storage server, wich is mounted in the webserver via NFS. 95% of the 
files that I serve are images, and the format of the file name is 
{number}.png.

I have these images all together in a single directory, and there was 
about 4 million files in this folder.

I wanto to change this directory structure to something more secure and 
dynamic, to permit an easier way to scale and backup these files.

My questions are:

- When the quantity of files will start to become a bottleneck for my 
filesystem? ( they are stored in partition with ext3)

- When the quantity of files will start to become a bottleneck for my OS?

- Suggestions?

Thanks

[]s
    Fábio Jr.