To undestand what XSendFile is and its usefulness, go here : Media centre.
Apache provides the feature through the mod_xsendfile module. Then, the .htaccess must be updated to enable it:
# Post-installation optimisation
<IfModule xsendfile_module>
XSendFile On
# Replace "novius-os-install-dir" by the real Novius OS installed directory
XSendFilePath /novius-os-install-dir/local/data
</IfModule>
Novius OS know when the module is enabled automatically and enable the XSendFile feature accordingly.
nginx provides the feature natively, but the header used is X-Accel-Redirect. In that case, you need to edit the config.php file to tell Novius OS the appropriate header :
<?php
return array(
// ...
'novius-os' => array(
// ...
'use_xsendfile' => 'X-Accel-Redirect',
),
);