magento: fast_backend vs slow_backend vs backend - What is going on here?

Heard some talk about this being something that can be set in apt/etc/local.xml but I didnt see any of it there by default.. Maybe you can add it?开发者_JS百科

Anyway. It was described to me that the fast_backend gets some of the magento stuff while the slow_backend get the other stuff and if fast_backend fails, then it will failover to slow_backend.

Where do I set these options? What is stored in fast_backend? What is stored in slow_backend?

What is the option "backend" for and what is stored there?

---

take a look at the local.xml.additional in the same folder hints on how to configure it properly.

also, http://www.fabrizio-branca.de/magento-caching-internals.html gives a good overview about the magento caches.