Fujitsu MHY2120BH manual Reliability, Mean time between failures Mtbf, Mean time to repair Mttr

Device Overview

1.7	Reliability
(1)	Mean time between failures (MTBF)
		Conditions of 300,000 h	Power-on time	250H/month or less 3000H/years
				or less
			Operating time	20 % or less of power-on time
			Temperature	5 to 60 °C (Disk Enclosure surface)
			Humidity	8 to 90 % (ambient)
				But humidity bulb temperature
				29 °C or less
		MTBF is defined as follows:
		Total operation time in all fields
		MTBF=		(H)

number of device failure in all fields (*1)

*1 "Disk drive defects" refers to defects that involve repair, readjustment, or replacement. Disk drive defects do not include failures caused by external factors, such as damage caused by handling, inappropriate operating environments, defects in the power supply host system, or interface cable.

(2) Mean time to repair (MTTR)

The mean time to repair (MTTR) is 30 minutes or less, if repaired by a specialist maintenance staff member.

(3) Service life

In situations where management and handling are correct, the disk drive requires no overhaul for five years when the DE surface temperature is less than 48 °C. When the DE surface temperature exceeds 48 °C, the disk drives requires no overhaul for five years or 20,000 hours of operation, whichever occurs first. Refer to item (3) in Subsection 3.2 for the measurement point of the DE surface temperature. The operating conditions of Service life are based on the equal conditions with MTBF.

(4) Data assurance in the event of power failure

Except for the data block being written to, the data on the disk media is assured in the event of any power supply abnormalities. This does not include power supply abnormalities during disk media initialization (formatting) or processing of defects (alternative block assignment).

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