diff --git a/library/Zend/Cache/Storage/Adapter/AbstractZendServer.php b/library/Zend/Cache/Storage/Adapter/AbstractZendServer.php
index e81c10b03f7..3c48de290ac 100644
--- a/library/Zend/Cache/Storage/Adapter/AbstractZendServer.php
+++ b/library/Zend/Cache/Storage/Adapter/AbstractZendServer.php
@@ -41,10 +41,10 @@ abstract class AbstractZendServer extends AbstractAdapter
      */
     protected function internalGetItem(& $normalizedKey, & $success = null, & $casToken = null)
     {
-        $prefix      = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR;
-        $internalKey = $prefix . $normalizedKey;
+        $namespace   = $this->getOptions()->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . self::NAMESPACE_SEPARATOR;
 
-        $result = $this->zdcFetch($internalKey);
+        $result = $this->zdcFetch($prefix . $normalizedKey);
         if ($result === false) {
             $success = false;
             $result  = null;
@@ -65,16 +65,20 @@ protected function internalGetItem(& $normalizedKey, & $success = null, & $casTo
      */
     protected function internalGetItems(array & $normalizedKeys)
     {
-        $prefix  = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR;
-        $prefixL = strlen($prefix);
+        $namespace = $this->getOptions()->getNamespace();
+        if ($namespace === '') {
+            return $this->zdcFetchMulti($normalizedKeys);
+        }
 
+        $prefix       = $namespace . self::NAMESPACE_SEPARATOR;
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
         }
 
-        $fetch  = $this->zdcFetchMulti($internalKeys);
-        $result = array();
+        $fetch   = $this->zdcFetchMulti($internalKeys);
+        $result  = array();
+        $prefixL = strlen($prefix);
         foreach ($fetch as $k => & $v) {
             $result[ substr($k, $prefixL) ] = $v;
         }
@@ -91,8 +95,8 @@ protected function internalGetItems(array & $normalizedKeys)
      */
     protected function internalHasItem(& $normalizedKey)
     {
-
-        $prefix = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR;
+        $namespace = $this->getOptions()->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . self::NAMESPACE_SEPARATOR;
         return  ($this->zdcFetch($prefix . $normalizedKey) !== false);
     }
 
@@ -105,16 +109,20 @@ protected function internalHasItem(& $normalizedKey)
      */
     protected function internalHasItems(array & $normalizedKeys)
     {
-        $prefix  = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR;
-        $prefixL = strlen($prefix);
+        $namespace = $this->getOptions()->getNamespace();
+        if ($namespace === '') {
+            return array_keys($this->zdcFetchMulti($normalizedKeys));
+        }
 
+        $prefix       = $namespace . self::NAMESPACE_SEPARATOR;
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
         }
 
-        $fetch  = $this->zdcFetchMulti($internalKeys);
-        $result = array();
+        $fetch   = $this->zdcFetchMulti($internalKeys);
+        $result  = array();
+        $prefixL = strlen($prefix);
         foreach ($fetch as $internalKey => & $value) {
             $result[] = substr($internalKey, $prefixL);
         }
@@ -134,16 +142,21 @@ protected function internalHasItems(array & $normalizedKeys)
      */
     protected function internalGetMetadatas(array & $normalizedKeys)
     {
-        $prefix  = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR;
-        $prefixL = strlen($prefix);
+        $namespace = $this->getOptions()->getNamespace();
+        if ($namespace === '') {
+            $result = $this->zdcFetchMulti($normalizedKeys);
+            return array_fill_keys(array_keys($result), array());
+        }
 
+        $prefix       = $namespace . self::NAMESPACE_SEPARATOR;
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
         }
 
-        $fetch  = $this->zdcFetchMulti($internalKeys);
-        $result = array();
+        $fetch   = $this->zdcFetchMulti($internalKeys);
+        $result  = array();
+        $prefixL = strlen($prefix);
         foreach ($fetch as $internalKey => $value) {
             $result[ substr($internalKey, $prefixL) ] = array();
         }
@@ -163,9 +176,10 @@ protected function internalGetMetadatas(array & $normalizedKeys)
      */
     protected function internalSetItem(& $normalizedKey, & $value)
     {
-        $options = $this->getOptions();
-        $internalKey = $options->getNamespace() . self::NAMESPACE_SEPARATOR . $normalizedKey;
-        $this->zdcStore($internalKey, $value, $options->getTtl());
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . self::NAMESPACE_SEPARATOR;
+        $this->zdcStore($prefix . $normalizedKey, $value, $options->getTtl());
         return true;
     }
 
@@ -178,8 +192,9 @@ protected function internalSetItem(& $normalizedKey, & $value)
      */
     protected function internalRemoveItem(& $normalizedKey)
     {
-        $internalKey = $this->getOptions()->getNamespace() . self::NAMESPACE_SEPARATOR . $normalizedKey;
-        return $this->zdcDelete($internalKey);
+        $namespace = $this->getOptions()->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . self::NAMESPACE_SEPARATOR;
+        return $this->zdcDelete($prefix . $normalizedKey);
     }
 
     /* status */
diff --git a/library/Zend/Cache/Storage/Adapter/Apc.php b/library/Zend/Cache/Storage/Adapter/Apc.php
index 6b8f29500c6..870f880df9d 100644
--- a/library/Zend/Cache/Storage/Adapter/Apc.php
+++ b/library/Zend/Cache/Storage/Adapter/Apc.php
@@ -109,7 +109,7 @@ public function getOptions()
      */
     public function getTotalSpace()
     {
-        if ($this->totalSpace !== null) {
+        if ($this->totalSpace === null) {
             $smaInfo = apc_sma_info(true);
             $this->totalSpace = $smaInfo['num_seg'] * $smaInfo['seg_size'];
         }
@@ -139,9 +139,14 @@ public function getAvailableSpace()
      */
     public function getIterator()
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $pattern = '/^' . preg_quote($prefix, '/') . '/';
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = '';
+        $pattern   = null;
+        if ($namespace !== '') {
+            $prefix  = $namespace . $options->getNamespaceSeparator();
+            $pattern = '/^' . preg_quote($prefix, '/') . '/';
+        }
 
         $baseIt = new BaseApcIterator('user', $pattern, 0, 1, \APC_LIST_ACTIVE);
         return new ApcIterator($this, $baseIt, $prefix);
@@ -169,9 +174,14 @@ public function flush()
      */
     public function clearByNamespace($namespace)
     {
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
         $options = $this->getOptions();
         $prefix  = $namespace . $options->getNamespaceSeparator();
-        $pattern = '/^' . preg_quote($prefix, '/') . '+/';
+        $pattern = '/^' . preg_quote($prefix, '/') . '/';
         return apc_delete(new BaseApcIterator('user', $pattern, 0, 1, \APC_LIST_ACTIVE));
     }
 
@@ -185,9 +195,15 @@ public function clearByNamespace($namespace)
      */
     public function clearByPrefix($prefix)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator() . $prefix;
-        $pattern = '/^' . preg_quote($prefix, '/') . '+/';
+        $prefix = (string) $prefix;
+        if ($prefix === '') {
+            throw new Exception\InvalidArgumentException('No prefix given');
+        }
+
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $nsPrefix  = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
+        $pattern = '/^' . preg_quote($nsPrefix . $prefix, '/') . '/';
         return apc_delete(new BaseApcIterator('user', $pattern, 0, 1, \APC_LIST_ACTIVE));
     }
 
@@ -205,7 +221,8 @@ public function clearByPrefix($prefix)
     protected function internalGetItem(& $normalizedKey, & $success = null, & $casToken = null)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $result      = apc_fetch($internalKey, $success);
 
@@ -226,9 +243,13 @@ protected function internalGetItem(& $normalizedKey, & $success = null, & $casTo
      */
     protected function internalGetItems(array & $normalizedKeys)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return apc_fetch($normalizedKeys);
+        }
 
+        $prefix       = $namespace . $options->getNamespaceSeparator();
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
@@ -255,8 +276,9 @@ protected function internalGetItems(array & $normalizedKeys)
      */
     protected function internalHasItem(& $normalizedKey)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         return apc_exists($prefix . $normalizedKey);
     }
 
@@ -269,9 +291,14 @@ protected function internalHasItem(& $normalizedKey)
      */
     protected function internalHasItems(array & $normalizedKeys)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            // array_filter with no callback will remove entries equal to FALSE
+            return array_keys(array_filter(apc_exists($normalizedKeys)));
+        }
 
+        $prefix       = $namespace . $options->getNamespaceSeparator();
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
@@ -299,7 +326,8 @@ protected function internalHasItems(array & $normalizedKeys)
     protected function internalGetMetadata(& $normalizedKey)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
 
         // @see http://pecl.php.net/bugs/bug.php?id=22564
@@ -337,12 +365,16 @@ protected function internalGetMetadatas(array & $normalizedKeys)
             $keysRegExp[] = preg_quote($normalizedKey, '/');
         }
 
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $regexp  = '/^' . preg_quote($prefix, '/') . '(' . implode('|', $keysRegExp) . ')' . '$/';
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            $pattern = '/^(' . implode('|', $keysRegExp) . ')' . '$/';
+        } else {
+            $prefix  = $namespace . $options->getNamespaceSeparator();
+            $pattern = '/^' . preg_quote($prefix, '/') . '(' . implode('|', $keysRegExp) . ')' . '$/';
+        }
         $format  = \APC_ITER_ALL ^ \APC_ITER_VALUE ^ \APC_ITER_TYPE ^ \APC_ITER_REFCOUNT;
-
-        $it      = new BaseApcIterator('user', $regexp, $format, 100, \APC_LIST_ACTIVE);
+        $it      = new BaseApcIterator('user', $pattern, $format, 100, \APC_LIST_ACTIVE);
         $result  = array();
         $prefixL = strlen($prefix);
         foreach ($it as $internalKey => $metadata) {
@@ -371,7 +403,8 @@ protected function internalGetMetadatas(array & $normalizedKeys)
     protected function internalSetItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $ttl         = $options->getTtl();
 
@@ -394,9 +427,13 @@ protected function internalSetItem(& $normalizedKey, & $value)
      */
     protected function internalSetItems(array & $normalizedKeyValuePairs)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return array_keys(apc_store($normalizedKeyValuePairs, null, $options->getTtl()));
+        }
 
+        $prefix                = $namespace . $options->getNamespaceSeparator();
         $internalKeyValuePairs = array();
         foreach ($normalizedKeyValuePairs as $normalizedKey => &$value) {
             $internalKey = $prefix . $normalizedKey;
@@ -426,7 +463,8 @@ protected function internalSetItems(array & $normalizedKeyValuePairs)
     protected function internalAddItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $ttl         = $options->getTtl();
 
@@ -453,9 +491,13 @@ protected function internalAddItem(& $normalizedKey, & $value)
      */
     protected function internalAddItems(array & $normalizedKeyValuePairs)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return array_keys(apc_add($normalizedKeyValuePairs, null, $options->getTtl()));
+        }
 
+        $prefix                = $namespace . $options->getNamespaceSeparator();
         $internalKeyValuePairs = array();
         foreach ($normalizedKeyValuePairs as $normalizedKey => $value) {
             $internalKey = $prefix . $normalizedKey;
@@ -485,14 +527,15 @@ protected function internalAddItems(array & $normalizedKeyValuePairs)
     protected function internalReplaceItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
-        $ttl         = $options->getTtl();
 
         if (!apc_exists($internalKey)) {
             return false;
         }
 
+        $ttl = $options->getTtl();
         if (!apc_store($internalKey, $value, $ttl)) {
             $type = is_object($value) ? get_class($value) : gettype($value);
             throw new Exception\RuntimeException(
@@ -512,10 +555,10 @@ protected function internalReplaceItem(& $normalizedKey, & $value)
      */
     protected function internalRemoveItem(& $normalizedKey)
     {
-        $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
-        $internalKey = $prefix . $normalizedKey;
-        return apc_delete($internalKey);
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
+        return apc_delete($prefix . $normalizedKey);
     }
 
     /**
@@ -527,9 +570,13 @@ protected function internalRemoveItem(& $normalizedKey)
      */
     protected function internalRemoveItems(array & $normalizedKeys)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return apc_delete($normalizedKeys);
+        }
 
+        $prefix       = $namespace . $options->getNamespaceSeparator();
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
@@ -557,7 +604,8 @@ protected function internalRemoveItems(array & $normalizedKeys)
     protected function internalIncrementItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $ttl         = $options->getTtl();
         $value       = (int) $value;
@@ -588,7 +636,8 @@ protected function internalIncrementItem(& $normalizedKey, & $value)
     protected function internalDecrementItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $value       = (int) $value;
         $newValue    = apc_dec($internalKey, $value);
diff --git a/library/Zend/Cache/Storage/Adapter/Dba.php b/library/Zend/Cache/Storage/Adapter/Dba.php
index 64299dd9dae..364a0a0f2be 100644
--- a/library/Zend/Cache/Storage/Adapter/Dba.php
+++ b/library/Zend/Cache/Storage/Adapter/Dba.php
@@ -216,6 +216,11 @@ public function flush()
      */
     public function clearByNamespace($namespace)
     {
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
         $prefix  = $namespace . $this->getOptions()->getNamespaceSeparator();
         $prefixl = strlen($prefix);
         $result  = true;
@@ -247,10 +252,16 @@ public function clearByNamespace($namespace)
      */
     public function clearByPrefix($prefix)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator() . $prefix;
-        $prefixl = strlen($prefix);
-        $result  = true;
+        $prefix = (string) $prefix;
+        if ($prefix === '') {
+            throw new Exception\InvalidArgumentException('No prefix given');
+        }
+
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator() . $prefix;
+        $prefixL   = strlen($prefix);
+        $result    = true;
 
         $this->_open();
 
@@ -258,7 +269,7 @@ public function clearByPrefix($prefix)
             $recheck     = false;
             $internalKey = dba_firstkey($this->handle);
             while ($internalKey !== false && $internalKey !== null) {
-                if (substr($internalKey, 0, $prefixl) === $prefix) {
+                if (substr($internalKey, 0, $prefixL) === $prefix) {
                     $result = dba_delete($internalKey, $this->handle) && $result;
                     $recheck = true;
                 }
@@ -279,8 +290,9 @@ public function clearByPrefix($prefix)
      */
     public function getIterator()
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         return new DbaIterator($this, $this->handle, $prefix);
     }
@@ -315,12 +327,12 @@ public function optimize()
      */
     protected function internalGetItem(& $normalizedKey, & $success = null, & $casToken = null)
     {
-        $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
-        $internalKey = $prefix . $normalizedKey;
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         $this->_open();
-        $value = dba_fetch($internalKey, $this->handle);
+        $value = dba_fetch($prefix . $normalizedKey, $this->handle);
 
         if ($value === false) {
             $success = false;
@@ -341,12 +353,12 @@ protected function internalGetItem(& $normalizedKey, & $success = null, & $casTo
      */
     protected function internalHasItem(& $normalizedKey)
     {
-        $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
-        $internalKey = $prefix . $normalizedKey;
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         $this->_open();
-        return dba_exists($internalKey, $this->handle);
+        return dba_exists($prefix . $normalizedKey, $this->handle);
     }
 
     /* writing */
@@ -362,7 +374,8 @@ protected function internalHasItem(& $normalizedKey)
     protected function internalSetItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
 
         $this->_open();
@@ -384,7 +397,8 @@ protected function internalSetItem(& $normalizedKey, & $value)
     protected function internalAddItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
 
         $this->_open();
@@ -416,7 +430,8 @@ protected function internalAddItem(& $normalizedKey, & $value)
     protected function internalRemoveItem(& $normalizedKey)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
 
         $this->_open();
diff --git a/library/Zend/Cache/Storage/Adapter/Filesystem.php b/library/Zend/Cache/Storage/Adapter/Filesystem.php
index 41f69c64841..7c50c79f525 100644
--- a/library/Zend/Cache/Storage/Adapter/Filesystem.php
+++ b/library/Zend/Cache/Storage/Adapter/Filesystem.php
@@ -140,8 +140,9 @@ public function flush()
      */
     public function clearExpired()
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         $flags = GlobIterator::SKIP_DOTS | GlobIterator::CURRENT_AS_FILEINFO;
         $path  = $options->getCacheDir()
@@ -183,13 +184,18 @@ public function clearExpired()
      */
     public function clearByNamespace($namespace)
     {
-        $options  = $this->getOptions();
-        $nsPrefix = $namespace . $options->getNamespaceSeparator();
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
+        $options = $this->getOptions();
+        $prefix  = $namespace . $options->getNamespaceSeparator();
 
         $flags = GlobIterator::SKIP_DOTS | GlobIterator::CURRENT_AS_PATHNAME;
         $path = $options->getCacheDir()
-        . str_repeat(\DIRECTORY_SEPARATOR . $nsPrefix . '*', $options->getDirLevel())
-        . \DIRECTORY_SEPARATOR . $nsPrefix . '*';
+            . str_repeat(\DIRECTORY_SEPARATOR . $prefix . '*', $options->getDirLevel())
+            . \DIRECTORY_SEPARATOR . $prefix . '*';
         $glob = new GlobIterator($path, $flags);
 
         ErrorHandler::start();
@@ -198,7 +204,7 @@ public function clearByNamespace($namespace)
         }
         $error = ErrorHandler::stop();
         if ($error) {
-            throw new Exception\RuntimeException("Failed to remove file '{$pathname}'", 0, $error);
+            throw new Exception\RuntimeException("Failed to remove files of '{$path}'", 0, $error);
         }
 
         return true;
@@ -215,8 +221,14 @@ public function clearByNamespace($namespace)
      */
     public function clearByPrefix($prefix)
     {
-        $options  = $this->getOptions();
-        $nsPrefix = $options->getNamespace() . $options->getNamespaceSeparator();
+        $prefix = (string) $prefix;
+        if ($prefix === '') {
+            throw new Exception\InvalidArgumentException('No prefix given');
+        }
+
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $nsPrefix  = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         $flags = GlobIterator::SKIP_DOTS | GlobIterator::CURRENT_AS_PATHNAME;
         $path = $options->getCacheDir()
@@ -230,7 +242,7 @@ public function clearByPrefix($prefix)
         }
         $error = ErrorHandler::stop();
         if ($error) {
-            throw new Exception\RuntimeException("Failed to remove file '{$pathname}'", 0, $error);
+            throw new Exception\RuntimeException("Failed to remove files of '{$path}'", 0, $error);
         }
 
         return true;
@@ -302,9 +314,10 @@ public function clearByTags(array $tags, $disjunction = false)
             return true;
         }
 
-        $tagCount = count($tags);
-        $options  = $this->getOptions();
-        $prefix   = $options->getNamespace() . $options->getNamespaceSeparator();
+        $tagCount  = count($tags);
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
 
         $flags = GlobIterator::SKIP_DOTS | GlobIterator::CURRENT_AS_PATHNAME;
         $path  = $options->getCacheDir()
@@ -344,9 +357,10 @@ public function clearByTags(array $tags, $disjunction = false)
      */
     public function getIterator()
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $path    = $options->getCacheDir()
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
+        $path      = $options->getCacheDir()
             . str_repeat(\DIRECTORY_SEPARATOR . $prefix . '*', $options->getDirLevel())
             . \DIRECTORY_SEPARATOR . $prefix . '*.dat';
         return new FilesystemIterator($this, $path, $prefix);
@@ -362,13 +376,13 @@ public function getIterator()
      */
     public function optimize()
     {
-        $baseOptions = $this->getOptions();
-        if ($baseOptions->getDirLevel()) {
+        $options = $this->getOptions();
+        if ($options->getDirLevel()) {
+            $namespace = $options->getNamespace();
+            $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
+
             // removes only empty directories
-            $this->rmDir(
-                $baseOptions->getCacheDir(),
-                $baseOptions->getNamespace() . $baseOptions->getNamespaceSeparator()
-            );
+            $this->rmDir($options->getCacheDir(), $prefix);
         }
         return true;
     }
@@ -1234,10 +1248,11 @@ protected function rmDir($dir, $prefix)
      */
     protected function getFileSpec($normalizedKey)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $path    = $options->getCacheDir() . \DIRECTORY_SEPARATOR;
-        $level   = $options->getDirLevel();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
+        $path      = $options->getCacheDir() . \DIRECTORY_SEPARATOR;
+        $level     = $options->getDirLevel();
 
         $fileSpecId = $path . $prefix . $normalizedKey . '/' . $level;
         if ($this->lastFileSpecId !== $fileSpecId) {
diff --git a/library/Zend/Cache/Storage/Adapter/Memory.php b/library/Zend/Cache/Storage/Adapter/Memory.php
index 25251623d27..82c9faa3180 100644
--- a/library/Zend/Cache/Storage/Adapter/Memory.php
+++ b/library/Zend/Cache/Storage/Adapter/Memory.php
@@ -14,6 +14,7 @@
 use Zend\Cache\Exception;
 use Zend\Cache\Storage\AvailableSpaceCapableInterface;
 use Zend\Cache\Storage\Capabilities;
+use Zend\Cache\Storage\ClearByNamespaceInterface;
 use Zend\Cache\Storage\ClearByPrefixInterface;
 use Zend\Cache\Storage\ClearExpiredInterface;
 use Zend\Cache\Storage\FlushableInterface;
@@ -29,6 +30,7 @@
 class Memory extends AbstractAdapter implements
     AvailableSpaceCapableInterface,
     ClearByPrefixInterface,
+    ClearByNamespaceInterface,
     ClearExpiredInterface,
     FlushableInterface,
     IterableInterface,
@@ -174,6 +176,19 @@ public function clearExpired()
         return true;
     }
 
+    /* ClearByNamespaceInterface */
+
+    public function clearByNamespace($namespace)
+    {
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
+        unset($this->data[$namespace]);
+        return true;
+    }
+
     /* ClearByPrefixInterface */
 
     /**
@@ -184,6 +199,11 @@ public function clearExpired()
      */
     public function clearByPrefix($prefix)
     {
+        $prefix = (string) $prefix;
+        if ($prefix === '') {
+            throw new Exception\InvalidArgumentException('No prefix given');
+        }
+
         $ns = $this->getOptions()->getNamespace();
         if (!isset($this->data[$ns])) {
             return true;
diff --git a/library/Zend/Cache/Storage/Adapter/Session.php b/library/Zend/Cache/Storage/Adapter/Session.php
index eebb34810f7..fc0d2487f0b 100644
--- a/library/Zend/Cache/Storage/Adapter/Session.php
+++ b/library/Zend/Cache/Storage/Adapter/Session.php
@@ -117,6 +117,11 @@ public function flush()
      */
     public function clearByPrefix($prefix)
     {
+        $prefix = (string) $prefix;
+        if ($prefix === '') {
+            throw new Exception\InvalidArgumentException('No prefix given');
+        }
+
         $cntr = $this->getSessionContainer();
         $ns   = $this->getOptions()->getNamespace();
 
diff --git a/library/Zend/Cache/Storage/Adapter/WinCache.php b/library/Zend/Cache/Storage/Adapter/WinCache.php
index c81177d20ca..f3708b6bb8c 100644
--- a/library/Zend/Cache/Storage/Adapter/WinCache.php
+++ b/library/Zend/Cache/Storage/Adapter/WinCache.php
@@ -139,7 +139,8 @@ public function flush()
     protected function internalGetItem(& $normalizedKey, & $success = null, & $casToken = null)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $result      = wincache_ucache_get($internalKey, $success);
 
@@ -159,8 +160,13 @@ protected function internalGetItem(& $normalizedKey, & $success = null, & $casTo
      */
     protected function internalGetItems(array & $normalizedKeys)
     {
-        $options      = $this->getOptions();
-        $prefix       = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return wincache_ucache_get($normalizedKeys);
+        }
+
+        $prefix       = $namespace . $options->getNamespaceSeparator();
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
@@ -187,8 +193,9 @@ protected function internalGetItems(array & $normalizedKeys)
      */
     protected function internalHasItem(& $normalizedKey)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        $prefix    = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         return wincache_ucache_exists($prefix . $normalizedKey);
     }
 
@@ -202,7 +209,8 @@ protected function internalHasItem(& $normalizedKey)
     protected function internalGetMetadata(& $normalizedKey)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
 
         $info = wincache_ucache_info(true, $internalKey);
@@ -228,7 +236,8 @@ protected function internalGetMetadata(& $normalizedKey)
     protected function internalSetItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $ttl         = $options->getTtl();
 
@@ -251,19 +260,23 @@ protected function internalSetItem(& $normalizedKey, & $value)
      */
     protected function internalSetItems(array & $normalizedKeyValuePairs)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $prefixL = strlen($prefix);
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return wincache_ucache_set($normalizedKeyValuePairs, null, $options->getTtl());
+        }
 
+        $prefix                = $namespace . $options->getNamespaceSeparator();
         $internalKeyValuePairs = array();
-        foreach ($normalizedKeyValuePairs as $normalizedKey => $value) {
+        foreach ($normalizedKeyValuePairs as $normalizedKey => & $value) {
             $internalKey = $prefix . $normalizedKey;
-            $internalKeyValuePairs[$internalKey] = $value;
+            $internalKeyValuePairs[$internalKey] = & $value;
         }
 
         $result = wincache_ucache_set($internalKeyValuePairs, null, $options->getTtl());
 
         // remove key prefic
+        $prefixL = strlen($prefix);
         foreach ($result as & $key) {
             $key = substr($key, $prefixL);
         }
@@ -282,7 +295,8 @@ protected function internalSetItems(array & $normalizedKeyValuePairs)
     protected function internalAddItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         $ttl         = $options->getTtl();
 
@@ -305,10 +319,13 @@ protected function internalAddItem(& $normalizedKey, & $value)
      */
     protected function internalAddItems(array & $normalizedKeyValuePairs)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
-        $prefixL = strlen($prefix);
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            return wincache_ucache_add($normalizedKeyValuePairs, null, $options->getTtl());
+        }
 
+        $prefix                = $namespace . $options->getNamespaceSeparator();
         $internalKeyValuePairs = array();
         foreach ($normalizedKeyValuePairs as $normalizedKey => $value) {
             $internalKey = $prefix . $normalizedKey;
@@ -318,6 +335,7 @@ protected function internalAddItems(array & $normalizedKeyValuePairs)
         $result = wincache_ucache_add($internalKeyValuePairs, null, $options->getTtl());
 
         // remove key prefic
+        $prefixL = strlen($prefix);
         foreach ($result as & $key) {
             $key = substr($key, $prefixL);
         }
@@ -336,7 +354,8 @@ protected function internalAddItems(array & $normalizedKeyValuePairs)
     protected function internalReplaceItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         if (!wincache_ucache_exists($internalKey)) {
             return false;
@@ -363,7 +382,8 @@ protected function internalReplaceItem(& $normalizedKey, & $value)
     protected function internalRemoveItem(& $normalizedKey)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         return wincache_ucache_delete($internalKey);
     }
@@ -377,9 +397,14 @@ protected function internalRemoveItem(& $normalizedKey)
      */
     protected function internalRemoveItems(array & $normalizedKeys)
     {
-        $options = $this->getOptions();
-        $prefix  = $options->getNamespace() . $options->getNamespaceSeparator();
+        $options   = $this->getOptions();
+        $namespace = $options->getNamespace();
+        if ($namespace === '') {
+            $result = wincache_ucache_delete($normalizedKeys);
+            return ($result === false) ? $normalizedKeys : $result;
+        }
 
+        $prefix       = $namespace . $options->getNamespaceSeparator();
         $internalKeys = array();
         foreach ($normalizedKeys as $normalizedKey) {
             $internalKeys[] = $prefix . $normalizedKey;
@@ -410,7 +435,8 @@ protected function internalRemoveItems(array & $normalizedKeys)
     protected function internalIncrementItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         return wincache_ucache_inc($internalKey, (int) $value);
     }
@@ -426,7 +452,8 @@ protected function internalIncrementItem(& $normalizedKey, & $value)
     protected function internalDecrementItem(& $normalizedKey, & $value)
     {
         $options     = $this->getOptions();
-        $prefix      = $options->getNamespace() . $options->getNamespaceSeparator();
+        $namespace   = $options->getNamespace();
+        $prefix      = ($namespace === '') ? '' : $namespace . $options->getNamespaceSeparator();
         $internalKey = $prefix . $normalizedKey;
         return wincache_ucache_dec($internalKey, (int) $value);
     }
diff --git a/library/Zend/Cache/Storage/Adapter/ZendServerDisk.php b/library/Zend/Cache/Storage/Adapter/ZendServerDisk.php
index b33aef951b3..7ff9942266f 100644
--- a/library/Zend/Cache/Storage/Adapter/ZendServerDisk.php
+++ b/library/Zend/Cache/Storage/Adapter/ZendServerDisk.php
@@ -75,6 +75,11 @@ public function flush()
      */
     public function clearByNamespace($namespace)
     {
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
         return zend_disk_cache_clear($namespace);
     }
 
@@ -88,8 +93,8 @@ public function clearByNamespace($namespace)
      */
     public function getTotalSpace()
     {
-        if ($this->totalSpace !== null) {
-            $path = $this->getOptions()->getCacheDir();
+        if ($this->totalSpace === null) {
+            $path = ini_get('zend_datacache.disk.save_path');
 
             ErrorHandler::start();
             $total = disk_total_space($path);
@@ -97,6 +102,8 @@ public function getTotalSpace()
             if ($total === false) {
                 throw new Exception\RuntimeException("Can't detect total space of '{$path}'", 0, $error);
             }
+
+            $this->totalSpace = $total;
         }
         return $this->totalSpace;
     }
@@ -111,7 +118,7 @@ public function getTotalSpace()
      */
     public function getAvailableSpace()
     {
-        $path = $this->getOptions()->getCacheDir();
+        $path = ini_get('zend_datacache.disk.save_path');
 
         ErrorHandler::start();
         $avail = disk_free_space($path);
diff --git a/library/Zend/Cache/Storage/Adapter/ZendServerShm.php b/library/Zend/Cache/Storage/Adapter/ZendServerShm.php
index 1c9633d738d..13e6169e34c 100644
--- a/library/Zend/Cache/Storage/Adapter/ZendServerShm.php
+++ b/library/Zend/Cache/Storage/Adapter/ZendServerShm.php
@@ -65,6 +65,11 @@ public function flush()
      */
     public function clearByNamespace($namespace)
     {
+        $namespace = (string) $namespace;
+        if ($namespace === '') {
+            throw new Exception\InvalidArgumentException('No namespace given');
+        }
+
         return zend_shm_cache_clear($namespace);
     }
 
diff --git a/tests/ZendTest/Cache/Storage/Adapter/CommonAdapterTest.php b/tests/ZendTest/Cache/Storage/Adapter/CommonAdapterTest.php
index ace231e4384..0e46955f53f 100644
--- a/tests/ZendTest/Cache/Storage/Adapter/CommonAdapterTest.php
+++ b/tests/ZendTest/Cache/Storage/Adapter/CommonAdapterTest.php
@@ -402,8 +402,10 @@ public function testGetMetadatasReturnsEmptyArrayIfNonReadable()
         $this->assertEquals(array(), $this->_storage->getMetadatas(array('key')));
     }
 
-    public function testSetGetHasAndRemoveItem()
+    public function testSetGetHasAndRemoveItemWithoutNamespace()
     {
+        $this->_storage->getOptions()->setNamespace('');
+
         $this->assertTrue($this->_storage->setItem('key', 'value'));
         $this->assertEquals('value', $this->_storage->getItem('key'));
         $this->assertTrue($this->_storage->hasItem('key'));
@@ -413,8 +415,10 @@ public function testSetGetHasAndRemoveItem()
         $this->assertNull($this->_storage->getItem('key'));
     }
 
-    public function testSetGetHasAndRemoveItems()
+    public function testSetGetHasAndRemoveItemsWithoutNamespace()
     {
+        $this->_storage->getOptions()->setNamespace('');
+
         $items = array(
             'key1' => 'value1',
             'key2' => 'value2',
@@ -937,6 +941,16 @@ public function testClearByPrefix()
         $this->assertTrue($this->_storage->hasItem('test'));
     }
 
+    public function testClearByPrefixThrowsInvalidArgumentExceptionOnEmptyPrefix()
+    {
+        if (!($this->_storage instanceof ClearByPrefixInterface)) {
+            $this->markTestSkipped("Storage doesn't implement ClearByPrefixInterface");
+        }
+
+        $this->setExpectedException('Zend\Cache\Exception\InvalidArgumentException');
+        $this->_storage->clearByPrefix('');
+    }
+
     public function testClearByNamespace()
     {
         if (!($this->_storage instanceof ClearByNamespaceInterface)) {
@@ -971,6 +985,16 @@ public function testClearByNamespace()
         $this->assertFalse($this->_storage->hasItem('key2'));
     }
 
+    public function testClearByNamespaceThrowsInvalidArgumentExceptionOnEmptyNamespace()
+    {
+        if (!($this->_storage instanceof ClearByNamespaceInterface)) {
+            $this->markTestSkipped("Storage doesn't implement ClearByNamespaceInterface");
+        }
+
+        $this->setExpectedException('Zend\Cache\Exception\InvalidArgumentException');
+        $this->_storage->clearByNamespace('');
+    }
+
     public function testClearExpired()
     {
         if (!($this->_storage instanceof ClearExpiredInterface)) {
@@ -1049,7 +1073,7 @@ public function testGetTotalSpace()
         }
 
         $totalSpace = $this->_storage->getTotalSpace();
-        $this->assertGreaterThan(0, $totalSpace);
+        $this->assertGreaterThanOrEqual(0, $totalSpace);
 
         if ($this->_storage instanceof AvailableSpaceCapableInterface) {
             $availableSpace = $this->_storage->getAvailableSpace();