Seagate Elite 9, Product Manual

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20 Elite 9 Product Manual, Rev. C
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 report indicates 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. Unrecover-
able 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 Elite 9 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 500,000 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, 45°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 Elite 9 drive must provide
cooling of the electronics and head and disc assembly (HDA). You should
confirm that adequate cooling is provided using the temperature measure-
ment guidelines described below.
Orient the drive or direct 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 Elite 9 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.