Sharing cache directory of cakephp on multiple servers

We having been using multiple webservers for our cakephp application,

server architecture

now the problem is there are two cache directories , server 2 is clearing his cache before doing any insertion in his database. BUT server 1 doesn't know the about the database has been changed , so server 1 cached is not cleared

When new web request comes to server 2 , he creates new cache files and return good results. BUT when it comes to server 1 , he show same old results :( .

I wonder is there any way we can share the cache directory among various physical servers, without compromising with performance.

We may increase the web servers, so please recommend good long term solution for this

Thanks for reading