try replace select by switcher

app/UI/VmCreate/Sections/AdditionalDiskSection.php

@@ -64,11 +64,8 @@ class AdditionalDiskSection extends BaseSection implements ClientArea
         //backup
         if ($this->configuration()->isPermissionAdditionalDiskBackup())
         {
-            $field = new Select('additionalDiskBackup');
-            $field->setAvailableValues([
-                'on' => 'Enable',
-                'off'=>'Disable',
-            ]);
+            $field = new Switcher('additionalDiskBackup');
+            $field->setDefaultValue('off');
             $field->replaceClasses(['lu-col-md-6']);
             $this->addField($field);
         }