The Static driver saves all items as files on your web server, which works great for a single web server, and if Redis is not available to you. However, if you have multiple web servers, it is recommended to use Redis with Static enabled. This is very similar to Static caching where the entire contents of your pages are saved in Redis, but is better for multiple server enviroments because each server is using the same cache storage. Since the Static driver saves files to the server, you will have multiple instances of the same cached item. For example, if Jane comes to your site, and the load balancer sends her to server A, then John comes to your site and is sent to server B, John will not see the cached page that was created for Jane. Cache clearing also becomes more difficult because you will need to login to the control panel on each server to clear cache items.