If you need to use different caching strategies for your Rails.cache and your ActionController::Cache (used for fragment caching) just put the following in your config/environments/env.rb
file:
config.action_controller.perform_caching = true
# this is used for your Fragment cache
config.action_controller.cache_store = :file_store, 'action_controller_tore_path'
# this is used for Rails.cache
config.cache_store = :file_store, 'cache_store_path'