Best way to sync application servers on a load balanced web app?

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http://serverfault.com – I'm trying to figure out how to load balance an application, such as WordPress. My server array would look like this: Load Balancer. Database Server. 2 or more application servers. Most, if not all of the content will be stored in the database, so content won't be a problem, and deployments will also be solved by having both servers clone from a remote GIT repo, but what happens if someone uploads an image to one server? How would it get synced to the other? I'm guessing that I could do this with rSync, but I feel that that is kind of outdated. Any recommendations would be greatly appreci (HowTos)