Large Installation

[shalsaid]

Hello

we have a vbulletin installation that gets about 1.5 million pageviews per day

we use one apache server and two db servers one master (8 cpus 16G RAM)and the other is slave (8 CPUs 16 G RAM)

we use mysql 5

we use this confogration
// If you have multiple database backends, this is the information for your slave
// server. If you are not 100% sure you need to fill in this information,
// do not change any of the values here.
$config['SlaveServer']['servername'] = 'x.y.z.a';
$config['SlaveServer']['port'] = 3306;
$config['SlaveServer']['username'] = 'xxxxxxx';
$config['SlaveServer']['password'] = 'yyyyyyy';
$config['SlaveServer']['usepconnect'] = 0;

we have a problem that there is lag between the master and slave and sometimes locks on peak hours, which cause the server to be down

how can we scale the DB? if we use another slave i belive the locks will be worse since master need to synch two slaves.

I read that some people use memcache we installed a memcache server and configured the forum to connect to it
// ****** DATASTORE CACHE CONFIGURATION *****
// Here you can configure different methods for caching datastore items.
// vB_Datastore_Filecache - for using a cache file
// $config['Datastore']['class'] = 'vB_Datastore_Filecache';
// vB_Datastore_Memcached - for using a Memcache server
// It is also necessary to specify the hostname or IP address and the port the server is listening on
$config['Datastore']['class'] = 'vB_Datastore_Memcached';
$config['Misc']['memcacheserver'] = '10.0.0.1';
$config['Misc']['memcacheport'] = '11211';

we noticed that it just conume 60M of memcache only. how can we store more data in the datastore? can we store other stuff in the memcache

since i read that somepeople have two server of memcache. so there is a way to cahce more data

your help is appreciated

thanks
shadi