Seagate Cheetah 15K.5 SAS ST373455SS - Manual (Page 22)

16 Cheetah 15K.5 SAS Product Manual, Rev. E
5.1.3 Seek errors
A seek error is defined as a failure of the drive to position the heads to the addressed track. After detecting an
initial seek error, the drive automatically performs an error recovery process. If the error recovery process fails,
a seek positioning error (Error code = 15h or 02h) will be reported with a Hardware error (04h) in the Sense
Key. Recoverable seek errors are specified at Less than 10 errors in 10
8
seeks. Unrecoverable seek errors
(Sense Key = 04h) are classified as drive failures.
5.1.4 Interface errors
An interface error is defined as a failure of the receiver on a port to recover the data as transmitted by the
device port connected to the receiver. The error may be detected as a running disparity error, illegal code, loss
of word sync, or CRC error.
5.2 Reliability and service
You can enhance the reliability of Cheetah disc drives by ensuring that the drive receives adequate cooling.
Section 6.0 provides temperature measurements and other information that may be used to enhance the ser-
vice life of the drive. Section 8.2 provides recommended air-flow information.
5.2.1 Mean time between failure (MTBF)
The production disc drive shall achieve a MTBF of 1,400,000 hours when operated in an environment that
ensures the HDA case temperatures specified in Section 6.4 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 temperatures above the values shown 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.
MTBF = Estimate power-on operating hours in the period
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Number of drive failures 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 cal-
culated 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 is required.