driveReadsKBPerSec  = "reads_kb_per_sec"
	driveReadsAwait     = "reads_await"
	driveWritesPerSec   = "writes_per_sec"
	driveWritesKBPerSec = "writes_kb_per_sec"
	driveWritesAwait    = "writes_await"
	drivePercUtil       = "perc_util"
)

var (
	driveUsedBytesMD = NewGaugeMD(driveUsedBytes,
		"Total storage used on a drive in bytes", allDriveLabels...)
	driveFreeBytesMD = NewGaugeMD(driveFreeBytes,

	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"
	percUtil       MetricName = "perc_util"
	usedInodes     MetricName = "used_inodes"

	// network stats
	interfaceRxBytes  MetricName = "rx_bytes"
	interfaceRxErrors MetricName = "rx_errors"

		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 {
	storageInfo                              madmin.StorageInfo