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Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B
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6.1.3
Write errors
Write errors can occur as a result of media defects, environmental interference, or equipment malfunction. There-
fore, write errors are not predictable as a function of the number of bits passed.
If an unrecoverable write error occurs because of an equipment malfunction in the drive, the error is classified as
a failure affecting MTBF. Unrecoverable write errors are those which cannot be corrected within two attempts at
writing the record with a read verify after each attempt (excluding media defects).
6.1.4
Seek errors
A seek error is defined as a failure of the drive to position the heads to the addressed track. There shall 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 3 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. Ref. section 5.1.1.2 of SCSI-2 Interface Product Manual P/
N 77738479.
6.2
Reliability and service
6.2.1
Mean time between failure
The production disc drive shall achieve an MTBF of 500,000 hours when operated in a benign atmosphere at an
average disc drive ambient temperature of 95°F (35°C) or less as measured per this Product Specification,
paragraph 7.4.1. Short term excursions up to the specification limits of the operating environment will not affect
MTBF performance.
The following expression defines MTBF:
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 calculated on
a rolling average base for a minimum period of six months.
Drive failure means any stoppage or substandard performance caused by drive malfunction.
6.2.2
Preventive maintenance
No routine scheduled preventive maintenance shall be required.
6.2.3
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 (6.2.4).
Estimated power-on operating hours in the period
Number of drive failures in the period
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