var available,
	free,
	total;

JSON.parse(value).forEach(function(metric) {
	if (metric['name'] == 'node_filesystem_size_bytes'){
		total = parseFloat(metric['value']);
	} else if (metric['name'] == 'node_filesystem_free_bytes'){
		free = parseFloat(metric['value']);
	} else if (metric['name'] == 'node_filesystem_avail_bytes'){
		available = parseFloat(metric['value']);
	}
});
if ((total - free + available) <= 0){
	return 0;
} else {
	return (100 - 100 * available / (total - free + available));
}