Managing upload files in multiple servers(pawns)

Hi All, We have a site in php and two web servers(pawns) to balance the load. There is a page in the site through which user can upload images. When a user uploads an image, the request goes to only one of the two servers. So the image will be uploaded to only one server. How can we copy that image to other server? Do we need to transfer the image using scp or is there any easy way? I am afraid of getting the request to the other server for that image before I copy it? What steps do we need to take to avoid inconsistancies (if any) would be caused by this kind of a system? Please advice. --srinadh