librenms-librenms/includes/html/graphs/device/diskio_common.inc.php

<?php

$i = 1;

foreach (dbFetchRows('SELECT * FROM `ucd_diskio` AS U, `devices` AS D WHERE D.device_id = ? AND U.device_id = D.device_id', [$device['device_id']]) as $disk) {
    $rrd_filename = rrd_name($disk['hostname'], ['ucd_diskio', $disk['diskio_descr']]);
    if (rrdtool_check_rrd_exists($rrd_filename)) {
        $rrd_list[$i]['filename'] = $rrd_filename;
        $rrd_list[$i]['descr'] = $disk['diskio_descr'];
        $rrd_list[$i]['ds_in'] = $ds_in;
        $rrd_list[$i]['ds_out'] = $ds_out;
        $i++;
    }
}