[ic] Performance hit from having many images in one directory?

[John1]

At the moment we have all our item images in a single directory (and all the 
thumbnails in one directory).  There are currently only about 1000 items, 
but this could increase significantly as time goes on (especially as we tend 
to leave any images of old discontinued products there just in case search 
engines etc still have them catalogued).

We run the Linux ext3 filing system.  Is there a performance hit from 
storing loads of files in a single directory?  I am sure I read somewhere 
once that there *is* a performance hit, but I have no idea how many image 
files we would need to store in one directory before the performance 
implications became significant, bearing in mind that each page loads 
between 10 and 20 images from the thumbnails directory and 1 image from the 
main items directory?

Please can anyone enlighten me on this?  Thanks.