enable backupswitcher by default

app/UI/Disk/Forms/UpdateForm.php

@@ -56,7 +56,7 @@ class UpdateForm extends BaseForm implements ClientArea
         $backupSwitcher = $this->getField('backup');
         if ( parent::getFormData()['id'] == 'scsi0') {
             $backupSwitcher->addHtmlAttribute(':disabled', true);
-            $backupSwitcher->addHtmlAttribute(':checked', true);
+            $backupSwitcher->setValue('on');
         }
 
     }