How to host a forum with multiple web servers?
I notice that some forums are run by multiple web servers.
They offer choices for visitors from different regions so that they can enjoy a better speed when browsing.
e.g. Visitors from USA use www1 , visitors from Europe use www2
My question is: how to synchronize the contents and files between different web servers?
For the dynamic content, one database server can be setup. So that all php scripts on different web servers can retrieve from the same database source.
But then, in a real-time forum, how to synchronize the files between the web servers? For example, one user from www1 uploads a file. This file will go to www1's filesystem. How to make this file appears in www2's filesytem?
I can think of 'rsync' every minute between servers. But still it's not real-time, and there may be problems if sychronication can't be finished within the minute.
Any other implementations or hints on this issue? Many thanks.