here's a grep of ps aux on my dev server
498 1575 0.0 0.0 330852 152 ? Ssl Jun14 2:58 memcached -d -p 11211 -u memcached -m 64 -c 1024 -P /var/run/memcached/memcached.pid
498 6446 0.0 0.0 330852 152 ? Ssl Jul23 1:09 memcached -d -p 11212 -u memcached -m 64 -c 1024 -P /var/run/memcached-2/memcached-2.pid
You have to install one or both of that extensions to use memcached inside your application. (I recommend the Memcache(d) one.) After successfully installed the extension(s), check it on your server using the command below:
$ php -m | grep memcache
If you have both extensions, output would be:
$ php -m | grep memcache memcache memcached
In your case, Zend Framework trying to use memcache extension (not memcached) which is probably not installed on your box.