LastMinute: make(map[string]AccElem, len(p.apiLatencies)),
				APICalls:   make(map[string]uint64, len(p.apiCalls)),
			}
			for i, v := range p.apiLatencies {
				diskMetric.LastMinute[storageMetric(i).String()] = v.total()
			}
			for i := range p.apiCalls {
				diskMetric.APICalls[storageMetric(i).String()] = atomic.LoadUint64(&p.apiCalls[i])
			}
			return diskMetric, nil
		},
	)

// the number of calls of each API and the moving average of
// the duration of each API.
type DiskMetrics struct {
	LastMinute              map[string]AccElem `json:"apiLatencies,omitempty"`
	APICalls                map[string]uint64  `json:"apiCalls,omitempty"`
	TotalWaiting            uint32             `json:"totalWaiting,omitempty"`
	TotalErrorsAvailability uint64             `json:"totalErrsAvailability"`