Drush alias doesn't work
If your settings.php file is at /usr/share/nginx/www/drupal-7.16/sites/default/settings.php, then you should change your 'root' line as follows:

'root' =&gt; '/usr/share/nginx/www/drupal-7.16',


The way you have it, Drush is expecting that your Drupal root is at /usr/share/nginx/www/drupal-7.16/sites, which is to say that it is also expecting to find your settings.php file at /usr/share/nginx/www/drupal-7.16/sites/sites/default/settings.php. Take out the extra 'sites' as shown above, and it should work fine.