What are the different Cache Engines best used for?

Trying to get to grips with the different types of cache engines File, APC, Xcache, Memcache. A开发者_开发百科nybody know of any good resources/links?

Note I am using Linux, PHP and mysql

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There are 2 types of caching terminology thrown around in PHP.

First is an optcode cache: http://en.wikipedia.org/wiki/PHP_accelerator

Second is a data cache: http://simas.posterous.com/php-data-caching-techniques

A few of the technologies can cross boundaries into both realms, but the basics behind them are simple. The idea is: Keep as much data in ram and precompiled because compiling and HD seeks are very expensive processes. HD Seeks can be done to find a file to compile / query the DB to get data / looking for a temp file, and every time that happens it slows down the user experience.

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Memcached is generally the way to go, but it has some "features" such as once you save some data to t cache, it doesn't necessarily guarantee that it will be available later as it dynamically removes old caches to make way for new ones. It's also fairly basic, you'll need to roll your own system for handling timeouts and preventing cascading but it's all fairly simple. There's tons of info in the Memcached FAQ, or feel free to ask and I'll post some code examples. Memcached can also act as a session handler which is great if you have lots of users or more than one server.

Otherwise disc caching is good if you only have one server or don't mind generating separate caches of each server. Generally faster than memcached as it doesn't have the network overhead (unless you have memcached on the same server). There are plenty of good disc caching frameworks but probably the best are Pear Cache_Lite and APC.

APC also has the added advantage that it can cache your compiled PHP code which may help on high-performance websites.