Seagate ST15150N Product Manual - Page 32

Reliability and service

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22 6.1.3 6.2 6.2.1 6.2.2 ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D Seek errors A seek error is defined as a failure of the drive to position the heads at the addressed track. There must be no more than one recoverable seek error in 107 physical seek operations. After detecting an initial seek error, the drive automatically reseeks to the addressed track up to three times. If a reseek is successful, the extended sense reports a seek positioning error (15h), no seek complete error (02h), or track follow error (09h), and the sense key reports a recovered error (1h). If all three reseeks fail, a seek positioning error (15h) is reported with a medium (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 Section 5.1.1.2 of the SCSI-2 Interface Product Manual (part number 77738479). Reliability and service You can enhance the reliability of Barracuda 4 disc drives by ensuring that the drive receives adequate cooling. This section provides recommended air-flow information, temperature measurements, and other information that may be used to enhance the service life of the drive. Mean time between failures (MTBF) The production disc drive achieves an MTBF of 800,000 hours when operated in an average local disc drive ambient temperature of 95°F (35°C) or less. Short-term excursions up to the specification limits (122°F, 50°C) of the operating environment will not affect MTBF performance. The following expression defines MTBF: Estimated power-on operating hours in the period MTBF = Number of drive failures 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. Data is calculated on a rolling-average base for a minimum period of six months. Air flow The rack, cabinet, or drawer environment for the Barracuda 4 drive must provide cooling of the electronics and head and disc assembly (HDA). You should confirm that adequate cooling is provided using the temperature measurement guidelines described below. Orient the drive or direct the air flow so that the least amount of air-flow resistance is created while providing air flow to the electronics and HDA. Also, choose the shortest possible path between the air inlet and exit to minimize the travel length of air heated by the Barracuda 4 drive and other heat sources within the rack, cabinet, or drawer environment. Possible air-flow patterns are shown in Figure 6. Create the air-flow patterns by using one or more fans, either forcing or drawing air as shown in the illustrations. Other air-flow patterns are acceptable as long as the temperature measurement guidelines are met.

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22
ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D
6.1.3
Seek errors
A seek error is defined as a failure of the drive to position the heads at the
addressed track. There must be no more than one recoverable seek error in
10
7
physical seek operations. After detecting an initial seek error, the drive
automatically reseeks to the addressed track up to three times. If a reseek
is successful, the extended sense reports a seek positioning error (15h), no
seek complete error (02h), or track follow error (09h), and the sense key
reports a recovered error (1h). If all three reseeks fail, a seek positioning error
(15h) is reported with a medium (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 Section 5.1.1.2 of
the
SCSI-2 Interface Product Manual
(part number 77738479).
6.2
Reliability and service
You can enhance the reliability of Barracuda 4 disc drives by ensuring that
the drive receives adequate cooling. This section provides recommended
air-flow information, temperature measurements, and other information that
may be used to enhance the service life of the drive.
6.2.1
Mean time between failures (MTBF)
The production disc drive achieves an MTBF of 800,000 hours when
operated in an average local disc drive ambient temperature
of 95°F (35°C)
or less. Short-term excursions up to the specification limits (122°F, 50°C)
of the operating environment will not affect MTBF performance.
The following expression defines MTBF:
MTBF
=
Estimated power-on operating hours in the period
Number of drive failures 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.
Data is calculated on a rolling-average base for a minimum period of six
months.
6.2.2
Air flow
The rack, cabinet, or drawer environment for the Barracuda 4 drive must
provide cooling of the electronics and head and disc assembly (HDA). You
should confirm that adequate cooling is provided using the temperature
measurement guidelines described below.
Orient the drive or direct the air flow so that the least amount of air-flow
resistance is created while providing air flow to the electronics and HDA.
Also, choose the shortest possible path between the air inlet and exit to
minimize the travel length of air heated by the Barracuda 4 drive and other
heat sources within the rack, cabinet, or drawer environment.
Possible air-flow patterns are shown in Figure 6. Create the air-flow patterns
by using one or more fans, either forcing or drawing air as shown in the
illustrations. Other air-flow patterns are acceptable as long as the tempera-
ture measurement guidelines are met.