Write Errors; Seek Errors; Reliability And Service; Mean Time Between Failure - Seagate ST11200N Product Manual

20
______________________________________________________________________________________
6.1.3

Write errors

Write errors can occur as a result of media defects, environmental interference, or equipment malfunction.
Therefore, 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 classi-
fied 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 unrecov-
erable 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 200,000 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 Specifi-
cation, 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 permit-
ted during the lifetime (6.2.4).
Product Manual - Hawk 1 Family SCSI-2 (Volume 1), Rev. D
Estimated power-on operating hours in the period
Number of drive failures in the period