title: 2 seperate Magento installs sometimes using each others cache - possible Memcached issue
body: <p>I have several Magento sites running on my dedicated server. 2 of which are configured to use memcached like so:</p>
  
  <pre><code>&lt;cache&gt;
      &lt;prefix&gt;alphanumeric&lt;/prefix&gt;
      &lt;backend&gt;memcached&lt;/backend&gt;
      &lt;memcached&gt;
          &lt;servers&gt;
              &lt;server&gt;
                  &lt;host&gt;&lt;![CDATA[127.0.0.1]]&gt;&lt;/host&gt;
                  &lt;port&gt;&lt;![CDATA[11211]]&gt;&lt;/port&gt;
                  &lt;persistent&gt;&lt;![CDATA[1]]&gt;&lt;/persistent&gt;
              &lt;/server&gt;
          &lt;/servers&gt;
      &lt;compression&gt;&lt;![CDATA[0]]&gt;&lt;/compression&gt;
      &lt;cache_dir&gt;&lt;![CDATA[]]&gt;&lt;/cache_dir&gt;
      &lt;hashed_directory_level&gt;&lt;![CDATA[]]&gt;&lt;/hashed_directory_level&gt;
      &lt;hashed_directory_umask&gt;&lt;![CDATA[]]&gt;&lt;/hashed_directory_umask&gt;
      &lt;file_name_prefix&gt;&lt;![CDATA[]]&gt;&lt;/file_name_prefix&gt;
    &lt;/memcached&gt;
  &lt;/cache&gt; 
  </code></pre>
  
  <p>(both use this excact code in etc/local.xml)</p>
  
  <p>Sometimes one of the sites starts to use/see the others cache. Flushing the cache within Magento sorts everything out again for a week or two.</p>
  
  <p>anyone know what might be causing this? I'm wondering whether I need to set the prefix differently for each Magento site perhaps?</p>
  
  <p>Thanks</p>