Is it for dynamic contents or static files?
Anyway, it is hard to do with either one. My suggestion is to avoid distributing the same file on multiple servers if you can. With LSWS, you probably don't need to do, one server should be more than enough to serve static file with any kind of volume. Just make sure your load balancer forward requests to the same file to the same backend server if there is one.
If you mixed static and dynamic content together on your backend servers, I suggest you to serve static file from a dedicate subdomain from one dedicate server.