Seek Errors; Reliability And Service; Mean Time Between Failure; Preventive Maintenance - Seagate ST3146854LC - Cheetah 146.8 GB Hard Drive User Manual

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
(Sense Key = 04h) are classified as drive failures.
5.2

Reliability and service

You can enhance the reliability of Cheetah 15K.4 SCSI disc drives by ensuring that the drive receives ade-
quate cooling. Section 6.0 provides temperature measurements and other information that may be used to
enhance the service life of the drive. Section 8.3 provides recommended air-flow information.
5.2.1

Mean time between failure

The production disc drive shall achieve an 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 per measurement 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 shall be required.
5.2.3

Hot plugging Cheetah 15K.4 SCSI disc drives

The ANSI SPI-4 document defines the physical requirements for removal and insertion of SCSI devices on the
SCSI bus. Four cases are addressed. The cases are differentiated by the state of the SCSI bus when the
removal or insertion occurs.
Case 1 - All bus devices powered off during removal or insertion
Case 2 - RST signal asserted continuously during removal or insertion
Case 3 - Current I/O processes not allowed during insertion or removal
18
= Estimated power-on operating hours in the period
Number of drive failures in the period
Cheetah 15K.4 SCSI Product Manual, Rev. D
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seeks. Unrecoverable seek errors