Memcached vs APC which one should I choose?

Question

I ready this article: http://www.mysqlperformanceblog.com/2006/09/27/apc-or-memcached/ from way back when.. I want to get the best cacheing engine available so that my application is really fast. Of cource I don't want to overcache but I want to at least choose the best thing out there. In that article it says memcached is slow and apc is fast so why is everyone choosing memcached?

http://framework.zend.com/manual/en/zend.cache.backends.html#zend.cache.backends.twolevels here is says "use a fast one (but limited) like Apc, Memcache... and a "slow" one like File, Sqlite..." do you think using Apc as the fast and memcache as the slow is a good idea?

Answer 1

Memcached if you need to preserve state across several web servers (if you're load balanced and it's important that what's in the cache is the same for all servers).

APC if you just need access to quick memory to read (& write) on a (or each) server.

Remember APC can also compile and speed up your script execution time. So you could for example be using APC for increased execution performance, while using memcached for cache storage.

Answer 2

Memcached is a distributed caching system, whereas APC is non-distributed - and mainly an opcode cache.

If (and only if) you have a web application which has to live on different webservers (loadbalancing), you have to use memcache for distributed caching. If not, just stick to APC and its cache.

You should always use an opcode cache, which APC is (also APC will get integrated into php6 iirc, so why not start using it now).

You can/should use both for different purposes.

Answer 3

Hey Thomaschaaf, I hope this is not tool late for you but please note that APC has some issues related to "user-cache". To make a long story short, when you set time-outs for cache entries, or if your apache crashes inside internal APC code (timeout, for example), then you may suffer some problems.

I have an entry about the issue here: http://nirlevy.blogspot.com/2009/06/apc-futexwait-lockdown-make-your-apache.html, and you should also read http://t3.dotgnu.info/blog/php/user-cache-timebomb.html (from one of the APC developers i think)