"Total number of offline drives in current MinIO server instance",
			nil, nil),
		prometheus.GaugeValue,
		float64(offlineDisks.Sum()),
	)

	// MinIO Total Disks per node
	ch <- prometheus.MustNewConstMetric(
		prometheus.NewDesc(
			prometheus.BuildFQName(minioNamespace, "drives", "total"),
			"Total number of drives for current MinIO server instance",
			nil, nil),

			storageLogOnceIf(GlobalContext, fmt.Errorf("Drive is not writable %s, %s", endpoint, hint), "log-fatal-errs")
		} else {
			logger.Fatal(config.ErrUnableToWriteInBackend(err).Hint("%s", hint), "Unable to initialize backend")
		}
	case errors.Is(err, errFaultyDisk):
		if !exit {
			storageLogOnceIf(GlobalContext, fmt.Errorf("Drive is faulty at %s, please replace the drive - drive will be offline", endpoint), "log-fatal-errs")

Joe Tsai <******@****.***> 1503105518 -0700

}

// Decode reads from readers, reconstructs data if needed and writes the data to the writer.
// A set of preferred drives can be supplied. In that case they will be used and the data reconstructed.
func (e Erasure) Decode(ctx context.Context, writer io.Writer, readers []io.ReaderAt, offset, length, totalLength int64, prefer []bool) (written int64, derr error) {
	if offset < 0 || length < 0 {

	// Storage operations.

	// Returns true if disk is online and its valid i.e valid format.json.
	// This has nothing to do with if the drive is hung or not responding.
	// For that individual storage API calls will fail properly. The purpose
	// of this function is to know if the "drive" has "format.json" or not
	// if it has a "format.json" then is it correct "format.json" or not.
	IsOnline() bool

		return true
	}
	return false
}

// diskHealthWrapper provides either a io.Reader or io.Writer
// that updates status of the provided tracker.
// Use through diskHealthReader or diskHealthWriter.
type diskHealthWrapper struct {
	tracker *healthDiskCtxValue
	r       io.Reader
	w       io.Writer
}

func (d *diskHealthWrapper) Read(p []byte) (int, error) {
	if d.r == nil {

- We limited the number of drives to 16 for erasure set because, erasure code shards more than 16 can become chatty and do not have any performance advantages. Additionally since 16 drive erasure set gives you tolerance of 8 drives per object by default which is plenty in any practical scenario.

		Subsystem: driveSubsystem,
		Name:      onlineTotal,
		Help:      "Total drives online in this cluster",
		Type:      gaugeMetric,
	}
}

func getClusterDrivesTotalMD() MetricDescription {
	return MetricDescription{
		Namespace: clusterMetricNamespace,
		Subsystem: driveSubsystem,
		Name:      total,
		Help:      "Total drives in this cluster",
		Type:      gaugeMetric,
	}
}

	if hr.Before.Drives[0].State != madmin.DriveStateMissing {
		t.Fatalf("Unexpected drive state: %v", hr.Before.Drives[0].State)
	}

	// Check the state of all other disks (should be ok)
	for i, h := range append(hr.Before.Drives[1:], hr.After.Drives...) {
		if h.State != madmin.DriveStateOk {
			t.Fatalf("Unexpected drive state (%d): %v", i+1, h.State)
		}
	}

two parity drives, 100 MiB file takes only approximately 114 MiB.

Below is a list of data/parity drives and corresponding _approximate_ storage space usage on a 16 drive MinIO deployment. The field _storage
usage ratio_ is simply the drive space used by the file after erasure-encoding, divided by actual file size.

| Total Drives (N) | Data Drives (D) | Parity Drives (P) | Storage Usage Ratio |