//count vfs.fs.inode.pfree
var inode_free;
var inode_total;
JSON.parse(value).forEach(function(metric) {
  if (metric['name'] == 'node_filesystem_files'){
      inode_total = metric['value'];
  } else if (metric['name'] == 'node_filesystem_files_free'){
      inode_free = metric['value'];
  }
});
return (inode_free/inode_total)*100;