cachevalue.Opts{ReturnLastGood: true},
		loadNodesUpDown)
}

type driveIOStatMetrics struct {
	readsPerSec    float64
	readsKBPerSec  float64
	readsAwait     float64
	writesPerSec   float64
	writesKBPerSec float64
	writesAwait    float64
	percUtil       float64
}

// storageMetrics - cached storage metrics.
type storageMetrics struct {

	if ioStats.readsPerSec > 0 {
		m.Set(driveReadsAwait, ioStats.readsAwait, labels...)
	}

	m.Set(driveWritesPerSec, ioStats.writesPerSec, labels...)
	m.Set(driveWritesKBPerSec, ioStats.writesKBPerSec, labels...)
	if ioStats.writesPerSec > 0 {
		m.Set(driveWritesAwait, ioStats.writesAwait, labels...)
	}

	m.Set(drivePercUtil, ioStats.percUtil, labels...)
}

const (
	resourceMetricsCollectionInterval = time.Minute
	resourceMetricsCacheInterval      = time.Minute

	// drive stats
	totalInodes    MetricName = "total_inodes"
	readsPerSec    MetricName = "reads_per_sec"
	writesPerSec   MetricName = "writes_per_sec"
	readsKBPerSec  MetricName = "reads_kb_per_sec"
	writesKBPerSec MetricName = "writes_kb_per_sec"
	readsAwait     MetricName = "reads_await"
	writesAwait    MetricName = "writes_await"