Seagate Savvio 10K Manual download pdf (Page 24)

Savvio SCSI Product Manual, Rev. D

5.1.2 Read errors

Before determination or measurement of read error rates:

• The data that is to be used for measurement of read error rates must be verified as being written correctly on

the media.

• All media defect induced errors must be excluded from error rate calculations.

5.1.3 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 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).

5.1.4 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 ten recoverable seek errors in 10

physical seek operations. After detecting an initial seek error, the

drive automatically performs an error recovery process. If the error recovery process fails, a seek positioning

error (15h) is reported with a 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 the SCSI Interface

Product Manual, part number 75789509, for Request Sense information.

5.2 Reliability and service

You can enhance the reliability of Savvio SCSI disc drives by ensuring that the drive receives adequate cool-

ing. Section 6 provides temperature measurements and other information that may be used to enhance the

service life of the drive. Section 8.2 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.

Estimated power-on operating hours in the period = MTBF per measurement period

Number of drive failures in the 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.

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Seagate Savvio 10K Manual Page 24