)

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"

	driveOnline                  = "online"

	driveOfflineCount = "offline_count"
	driveOnlineCount  = "online_count"
	driveCount        = "count"

	// iostat related
	driveReadsPerSec    = "reads_per_sec"
	driveReadsKBPerSec  = "reads_kb_per_sec"
	driveReadsAwait     = "reads_await"
	driveWritesPerSec   = "writes_per_sec"
	driveWritesKBPerSec = "writes_kb_per_sec"
	driveWritesAwait    = "writes_await"

| `minio_system_drive_online`                    | `gauge`   | Is it online?                                                      | `drive,set_index,drive_index,pool_index,server`     |
| `minio_system_drive_reads_per_sec`             | `gauge`   | Reads per second on a drive                                        | `drive,set_index,drive_index,pool_index,server`     |

| `minio_node_drive_total_inodes`      | Total inodes on a drive.                                 |
| `minio_node_drive_used_inodes`       | Total inodes used on a drive.                            |
| `minio_node_drive_reads_per_sec`     | Reads per second on a drive.                             |
| `minio_node_drive_reads_kb_per_sec`  | Kilobytes read per second on a drive.                    |

		return
	}
	return cachevalue.NewFromFunc(1*time.Minute,
		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.