Redis is one of the most popular caching mechanisms on the web. It keeps data in the server memory (RAM). To set Redis as a cache storage, you need to install and configure it on your server. Please, contact your system administrator or hosting provider for assistance in doing that. When Redis is installed, download pre-configured file or you can find it by its name "z_amfpclocal.xml" in the module folder. Then edit the file by adding Redis data in it and upload the file to app/etc folder. The result is that the database table "core_cache" shouldn't be increased.
We can say from our experience that MySQL Database is a very popular solution for the cache storage. The new records are created in the "core_cache" table with every new visited page. The solution is scalable. In case a store is replicated on several servers in order to balance site load, the database can be used as a common cache storage for numerous Magento nodes.
Moreover, it does not require any special skills to enable it.
File System is another solution to store cache. The cached data is stored in files on a disk. You can find them on a server in the magento_installation_folder/var/cache/ folder. The solution is available out of the box. So, there is no need to deal with configuration. In order to flush the cache it is required to remove all files from the var/cache/ with server access details.
To store cache in files you can just create a custom text file in the Magento root.
Memcached means "memory cached," which is simply caching resources in the memory. These resources can be data retrieved from API calls, database operations or even HTML pages. The data is stored in key/value pairs in the form of large hash tables. To use Memcache it should be installed and configured on a server. However, it is not a popular method of cache storage since it does not support tags and autoflush caching will not work as well. For example, when we save a product cache will not be cached automatically.