loadNodesUpDown := func(ctx context.Context) (v nodesOnline, err error) {
		v.Online, v.Offline = globalNotificationSys.GetPeerOnlineCount()
		return
	}
	return cachevalue.NewFromFunc(1*time.Minute,
		cachevalue.Opts{ReturnLastGood: true},
		loadNodesUpDown)
}

type driveIOStatMetrics struct {
	readsPerSec    float64
	readsKBPerSec  float64
	readsAwait     float64
	writesPerSec   float64

// RegisterRead register the metrics populator function to be used
// to populate new values upon cache invalidation.
func (g *MetricsGroupV2) RegisterRead(read func(context.Context) []MetricV2) {
	g.metricsCache = cachevalue.NewFromFunc(g.cacheInterval,
		cachevalue.Opts{ReturnLastGood: true},
		func(ctx context.Context) ([]MetricV2, error) {
			if g.metricsGroupOpts.dependGlobalObjectAPI {
				objLayer := newObjectLayerFn()