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Cheetah 9LP FC Product Manual, Rev. C
5.3
Reliability and service
The reliability of Cheetah 9LP FC disc drives can be enhanced by ensuring that the drive receives adequate
cooling. This section provides recommended air-flow information, temperature measurements, and other infor-
mation, which you can use to enhance the service life of the drive.
5.3.1
Mean time between failure (MTBF)
The production disc drive achieves an MTBF of 1,000,000 hours when operated in an environment that
ensures the case temperates specified in Section 8.4.1 are not exceeded. Short-term excursions up to the
specification limits of the operating environment will not affect MTBF performance. Operating the drive at case
temperatures above these values will adversely affect the drive's ability to meet specifications. See Section 6.4,
"Environmental limits" on page 21.
The following expression defines MTBF:
MTBF = Estimated power-on operating hours in the period
Estimated power-on operating hours means the estimated total power-on hours for all drives in service. Drive
failure means any stoppage or substandard performance caused by drive malfunction.
MTBF is based on the following criteria:
• 8,760 power-on hours per year
• 250 average on/off cycles per year
• Read/seek/write operation during 20% of power-on hours
• Operating at nominal voltages
• System provides adequate cooling to ensure the case temperatures specified in Figures 8 and 9 are not
exceeded. Short term excursions up to the specification limits of the operating environment will not affect
MTBF performance.
Data is calculated on a rolling-average base for a minimum period of six months.
A S.M.A.R.T. predictive failure indicates that the drive is deteriorating to an imminent failure and is considered
an MTBF hit.
Drive failure means any stoppage or substandard performance caused by drive malfunction.
5.3.2
Field failure rate vs time
The expected field failure rate is listed below. Drive utilization will vary. An estimate range of utilization is:
• 720 power-on hours (POH) per month
• 250 on/off cycles per year
• Read/seek/write operation 20% of POH
• System provides adequate cooling to ensure the case temperatures specified in Figures 8 and 9 are not
exceeded. Short term excursions up to the specification limits of the operating environment will not affect
MTBF performance.
Month
Parts per million (PPM)
1
2,364
2
1,422
3
1,403
4
1,391
5
1,317
6
1,255
7
1,162
8+
1,025
Number of drive failures in the period
15
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