diff --git a/README.md b/README.md
index bce9dfc..2b9add8 100755
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@ Then add parameters (probably in config.yml) for your servers, and options
 aequasi_cache:
     instances:
         default:
-          persistent: true
+          persistent: true # Boolean or persistent_id
           namespace: mc
           type: memcached
           hosts:
@@ -115,11 +115,11 @@ Here is an example usage of the service:
 $cache = $this->get( 'aequasi_cache.instance.default' );
 $key = 'test';
 if( $data = $cache->fetch( $key ) ) {
-	print_r( $data );
+    print_r( $data );
 } else {
-	/** @var $em \Doctrine\ORM\EntityManager */
-	$data = $em->find( 'AcmeDemoBundle:User', 1 );
-	$cache->save( $key, $data, 3600 );
+    /** @var $em \Doctrine\ORM\EntityManager */
+    $data = $em->find( 'AcmeDemoBundle:User', 1 );
+    $cache->save( $key, $data, 3600 );
 }
 ```
 
diff --git a/src/Cache/Memcached.php b/src/Cache/Memcached.php
index cf84f6b..be8a42f 100644
--- a/src/Cache/Memcached.php
+++ b/src/Cache/Memcached.php
@@ -22,7 +22,7 @@ public function addServer($host, $port, $weight = 0)
     {
         $serverList = $this->getServerList();
         foreach ($serverList as $server) {
-            if ($server == array('host' => $host, 'port' => $port, 'weight' => $weight)) {
+            if ($server['host'] === $host && $server['port'] === $port) {
                 return false;
             }
         }
diff --git a/src/DependencyInjection/Builder/ServiceBuilder.php b/src/DependencyInjection/Builder/ServiceBuilder.php
index eb5335d..bb993eb 100755
--- a/src/DependencyInjection/Builder/ServiceBuilder.php
+++ b/src/DependencyInjection/Builder/ServiceBuilder.php
@@ -157,9 +157,14 @@ public function createCacheInstance(Definition $service, $type, $id, array $inst
         if (empty($instance['id'])) {
             $cache = new Definition(self::$types[$type]['class']);
 
-            if (isset($instance['persistent']) && $instance['persistent'] === true) {
+            if (isset($instance['persistent']) && $instance['persistent'] !== false) {
+                if ($instance['persistent'] !== true) {
+                    $persistentId = $instance['persistent'];
+                } else {
+                    $persistentId = substr(md5(serialize($instance['hosts'])), 0, 5);
+                }
                 if ($type === 'memcached') {
-                    $cache->setArguments(array(serialize($instance['hosts'])));
+                    $cache->setArguments(array($persistentId));
                 }
                 if ($type === 'redis') {
                     self::$types[$type]['connect'] = 'pconnect';
@@ -167,15 +172,20 @@ public function createCacheInstance(Definition $service, $type, $id, array $inst
             }
 
             foreach ($instance['hosts'] as $config) {
-                $host    = empty($config['host']) ? 'localhost' : $config['host'];
-                $port    = empty($config['port']) ? 11211 : $config['port'];
+                $arguments = array(
+                    'host' => empty($config['host']) ? 'localhost' : $config['host'],
+                    'port' => empty($config['port']) ? 11211 : $config['port']
+                );
                 if ($type === 'memcached') {
-                    $thirdParam = is_null($config['weight']) ? 0 : $config['weight'];
+                    $arguments[] = is_null($config['weight']) ? 0 : $config['weight'];
                 } else {
-                    $thirdParam = is_null($config['timeout']) ? 0 : $config['timeout'];
+                    $arguments[] = is_null($config['timeout']) ? 0 : $config['timeout'];
+                    if (isset($persistentId)) {
+                        $arguments[] = $persistentId;
+                    }
                 }
 
-                $cache->addMethodCall(self::$types[$type]['connect'], array($host, $port, $thirdParam));
+                $cache->addMethodCall(self::$types[$type]['connect'], $arguments);
             }
             unset($config);
 
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 50a7b7e..170dff0 100755
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -83,9 +83,21 @@ private function getClustersNode()
                         ->defaultNull()
                         ->info("For Redis: Specify what database you want.")
                     ->end()
-                    ->booleanNode('persistent')
+                    ->scalarNode('persistent')
                         ->defaultNull()
-                        ->info("For Redis and Memcached: Specify if you want persistent connections.")
+                        ->beforeNormalization()
+                            ->ifTrue(
+                                function($v) { 
+                                    return $v === 'true' || $v === 'false'; 
+                                }
+                            )
+                            ->then(
+                                function($v) { 
+                                    return (bool) $v; 
+                                }
+                            )
+                        ->end()
+                        ->info("For Redis and Memcached: Specify the persistent id if you want persistent connections.")
                     ->end()
                     ->scalarNode('auth_password')
                         ->info("For Redis: Authorization info.")