@Juho, I use memcached. So I will switch to memcache. Hope that helps

@Jerome, could you share those 1-5 lines of code ?

in engine/settings.php

$CONFIG->memcache_prefix = "<some prefix>";

in engine/classes/ElggMemcache.php

private $namespace;

public function setNamespace($namespace = "default") {
        global $CONFIG;
        $prefix = "";

        if(!empty($CONFIG->memcache_prefix)) {
            $prefix = $CONFIG->memcache_prefix;
        }

        $this->namespace = $prefix . $namespace;
    }

public function getNamespace() {
        return $this->namespace;
    }

ps: I know more than 5 lines of code ;)

Thanks Jerome !

What I still don't understand, memcached is not supported is what Juho said. But without memcached there is no service listening to port 11211. How to use it then ?

@Gerard,

Juho was talking about the PHP module, not the service. There are two PHP modules, and you need to use php-memcache NOT php-memcached.

Ah :-0 

So use php-pecl-memcache and not php-pecl-memcached ! I am clear now. That was what I already used. I found the fix in moving widgets for memcache. Now let's test a multiple instances and give them separate name spaces.