Fujitsu MBA3147RC - Enterprise 147 GB Hard Drive Product Manual page 29

Note:
The MTBF is defined as:
MTBF =
Failure of the equipment means failure that requires repair, adjustments, or replacement.
Mishandling by the operator, failures due to bad environmental conditions, power trouble, host
system trouble, cable failures, or other failures not caused by the equipment are not considered.
(2) Mean Time To Repair (MTTR)
MTTR is the average time taken by a well-trained service mechanic to diagnose and repair an HDD
malfunction. The HDD is designed for a MTTR of 30 minutes or less.
(3) Service life
The service life under suitable conditions and treatment is as follows.
The service life is depending on the environment temperature. Therefore, the user must design the
system cabinet so that the average DE surface temperature is as low as possible.
DE surface temperature: from 5ºC to 40ºC
DE surface temperature: from 41ºC to 45ºC
DE surface temperature: from 46ºC to 50ºC
DE surface temperature: from 51ºC to 55ºC
DE surface temperature: from 56ºC to 60ºC
DE surface temperature: more than 60ºC or less than 5ºC
Even if the HDDs are used intermittently, the longest service life is 5 years.
The maximum storage period without turning the power on is six months.
Note:
The "average DE surface temperature" means the average temperature at the DE surface
throughout the year when the HDDs are operating.
C141-E252
Operating time (hours) at all field sites
The number of equipment failures from all field sites
2.1 Hardware Specifications
5 years
4.5 years
4 years
3.5 years
3 years
No guarantee (Keep the DE surface
temperature from 5 C to 60 C.)
25