Is there any gain using Memcached module when APC is running good on large Drupal 7 site (one server)

Question

I am successfully using the APC Cache module on my prod website (single server). APC is performing good, caching is done very well. I wonder could I gain anything more by implementing Memcache.

I tried it briefly on dev server, I see they can run one with another (Memcached Admin shows many hits in log). But i do not see any performance gain (haven't done precise measurements).

I should mention it is pretty large site, i use 256MB for APC (sometimes cache use is almost full), there is many content types, fields, nodes(over 10k), contrib modules (425 tables in db).

I am pasting at the end of the question my settings.php config (dev, prod just have not memcached implemented). There seems not much logic if i use cache_default_class twice, as Memcache will be used (declared lately).

So - have anyone used those two together when using one server? Is there any performance gain ? What are config ?

In addition, Memcached Readme.txt suggests using

$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';

but APC Readme.txt does not suggest that. I wonder why ?

Here is my code (using APC for Drupal backend cache)

# APC
$conf['cache_backends'] = array('sites/all/modules/contrib/apc/drupal_apc_cache.inc');
$conf['cache_default_class'] = 'DrupalAPCCache';
$conf['page_cache_without_database'] = TRUE;
$conf['page_cache_invoke_hooks'] = FALSE;

# Memcache
$conf['cache_backends'][] = 'sites/all/modules/contrib/memcache/memcache.inc';
$conf['cache_default_class'] = 'MemCacheDrupal';
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';

Answer 1

Putting the cache_form on the database is a good idea. I will help to prevent errors like this: http://drupal.org/node/500646

APC vs Memcache when it comes to the drupal cache mainly comes down to a persons preference. Mine is towards memcache because it allows for a multiple web head server setup. Performance wise APC will usually be a touch quicker, but my vote is still for memcache even on single server setups.