[horde] cache question

[Paras pradhan]

HI,

I am running horde 3.3.8  (IMP 4.3.7) and have tons of concurrent
users around 300+ active https tcp sessions. I am trying to tune the
horde and came across the cache driver.

Right now its none ( $conf['cache']['driver'] = 'none'; )

I think enabling this cache is highly recommended. Should I use file
or other driver? which one is recommened?

My system info:
CPU cores: 12 AMD opteron 2.2 GH
RAM: 12 GB
eaccelerator cache: 128M
memcached cache: 4GB

When 300 users hits the webserver (lighttpd with fastcgi) it really
becomes sluggish.

Any help is appreciated !
Thanks,
Paras.