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error (15h) is reported with a Medium error (3h) or Hardware error (4h) reported in the Sense Key. This is an
unrecoverable seek error. Unrecoverable seek errors are classified as failures for MTBF calculations. Refer to
the SCSI Interface Product Manual, part number 75789509, for Request Sense information.
5.2
Reliability and service
You can enhance the reliability of Cheetah 36ES disc drives by ensuring that the drive receives adequate cool-
ing. Section 6.0 provides temperature measurements and other information that may be used to enhance the
service life of the drive.
5.2.1
Mean time between failure
The production disc drive shall achieve an MTBF of 1,200,000 hours when operated in an environment that
ensures the case temperatures are not exceeded. Short-term excursions up to the specification limits of the
operating environment will not affect MTBF performance. Continual or sustained operation at case tempera-
tures above the values specified in Section 6.4.1 may degrade product reliability.
The MTBF target is specified as device power-on hours (POH) for all drives in service per failure.
Estimated power-on operating hours in the period
Estimated power-on operation hours means power-up hours per disc drive times the total number of disc drives
in service. Each disc drive shall have accumulated at least nine months of operation. Data shall be calculated
on a rolling average base for a minimum period of six months.
MTBF is based on the following assumptions:
• 8,760 power-on hours per year.
• 250 average on/off cycles per year.
• Operations at nominal voltages.
• Systems will provide adequate cooling to ensure the case temperatures specified in Section 6.4.1 are not
exceeded.
Drive failure means any stoppage or substandard performance caused by drive malfunction.
A S.M.A.R.T. predictive failure indicates that the drive is deteriorating to an imminent failure and is considered
an MTBF hit.
5.2.2
Preventive maintenance
No routine scheduled preventive maintenance shall be required.
5.2.3
Service life
The drive shall have a useful service life of five years. Depot repair or replacement of major parts is permitted
during the lifetime (see Section 5.2.4).
5.2.4
Service philosophy
Special equipment is required to repair the drive HDA. In order to achieve the above service life, repairs must
be performed only at a properly equipped and staffed service and repair facility. Troubleshooting and repair of
PCBs in the field is not recommended, because of the extensive diagnostic equipment required for effective
servicing. Also, there are no spare parts available for this drive. Drive warranty is voided if the HDA is opened.
5.2.5
Service tools
No special tools are required for site installation or recommended for site maintenance. Refer to Section 5.2.4.
The depot repair philosophy of the drive precludes the necessity for special tools. Field repair of the drive is not
practical since there are no user purchasable parts in the drive.
Cheetah 36ES Product Manual, Rev. A
=
MTBF per measurement period
Number of drive failures in the period
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