FUJITSU MHZ2250BJ - Manual (Page 35)

1.7 Reliability
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
Humidity
5 to 60
°C (Disk Enclosure surface)
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 require 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).
C141-E280 1-13