d := diskHealthTracker{
		lastSuccess: time.Now().UnixNano(),
		lastStarted: time.Now().UnixNano(),
	}
	d.status.Store(diskHealthOK)
	return &d
}

// logSuccess will update the last successful operation time.
func (d *diskHealthTracker) logSuccess() {
	atomic.StoreInt64(&d.lastSuccess, time.Now().UnixNano())
}

func (d *diskHealthTracker) isFaulty() bool {
	return d.status.Load() == diskHealthFaulty
}

)

func TestTierMetrics(t *testing.T) {
	tier := "WARM-1"
	globalTierMetrics.Observe(tier, 200*time.Millisecond)
	expSuccess := 10
	expFailure := 5
	for i := 0; i < expSuccess; i++ {
		globalTierMetrics.logSuccess(tier)
	}
	for i := 0; i < expFailure; i++ {
		globalTierMetrics.logFailure(tier)
	}
	metrics := globalTierMetrics.Report()
	var succ, fail float64
	for _, metric := range metrics {

	}, []string{"tier"}),
}

func (t *tierMetrics) Observe(tier string, dur time.Duration) {
	t.histogram.With(prometheus.Labels{"tier": tier}).Observe(dur.Seconds())
}

func (t *tierMetrics) logSuccess(tier string) {
	t.Lock()
	defer t.Unlock()

	stat := t.requestsCount[tier]
	stat.success++
	t.requestsCount[tier] = stat
}

func (t *tierMetrics) logFailure(tier string) {
	t.Lock()

			OutputBytes: bytes,
		}

		if err == nil {
			since := time.Since(startTime)
			op.TimeToResponseNS = since.Nanoseconds()
			globalTierMetrics.Observe(tier, since)
			globalTierMetrics.logSuccess(tier)
		} else {
			op.Error = err.Error()
			globalTierMetrics.logFailure(tier)
		}

		logger.GetReqInfo(ctx).AppendTags("tierStats", op)
	}
}