Configuring Page Caching in W3 Total Cache for Multiple Servers

If you have multiple hosting plans where one plan has root-level access, or if your WordPress hosting provider offers addons or bundles providing one of the following solutions, you may offload your in-memory caching to another server. This allows you to separate your actual site and caching solution between multiple servers to compliment each other, and allows for easier scaling to serve many users.

Page Caching Methods

Memcached

Memcached is a high-performance, distributed memory object caching system meant to speed up dynamic web applications by alleviating database load. It provides an in-memory key-value store for small chunks of arbitrary data (strings, objects) from the results of database calls, API calls, or page rendering.

Memcached is ideal for relatively small and static data, and as a result may be more efficient than Redis in smaller data sets. It is also multi-threaded, which may be a benefit when using a VPS or Dedicated Server with a large resource pool.

Redis

Redis is an in-memory data structure store which may be used as a database, cache, and message broker. Redis is somewhat of an industry-standard at the time of writing, and can be defined simply as a superset of Memcached when purely talking about similarities between each feature set.

Memcached + NGINX (Recommended)

This method is usually the fastest because cached data is always stored in memory and cached requests are processed without PHP. It combines the power of the Disk: Enhanced and Memcached options.

Caveats

Using an in-memory cache on another asset will assist with exceeding any disk-based performance issues, however you may run into issues if your traffic exceeds your available bandwidth as this requires fetching assets over a network. Offloading your caching to another server may not greatly decrease your site’s response time due to the extra HTTP transactions, though it will allow many more users to interact with your site simultaneously.

An additional concern is that requests to in-memory caches are generally handled by PHP scripts, which is considered to be slower than Disk: Enhanced.