Problems with memcached

Hi,

I used the module memcached in a multiple servers configuration. But, i've noticed that the flush cache doesn't work correctly, so i've made some unit test.

Here's my code :

$memcache = new Memcached();

echo 'set var in SERVER1 && SERVER 2 <br />';
$memcache->addServer('my_server1', 11211);
$memcache->addServer('my_server2', 11211);
$memcache->set('new_var', 'myvalue');

$memcache = new Memcached();
$memcache->addServer('my_server1', 11211);
echo 'from server1 '.$memcache->get('new_var').'<br />'; //return myvalue;

$memcache = new Memcached();
$memcache->addServer('my_server2', 11211);
echo 'from server2 '.$memcache->get('new_var').'<br />'; // return false

What's wrong with these simply code? Am I using memcached badly?

thanks for your helps!