Seagate ST373455FC Reliability and service, Seek errors, Interface errors, Preventive maintenance

5.1.3Seek errors

A seek error is defined as a failure of the drive to position the heads to the addressed track. After detecting an initial seek error, the drive automatically performs an error recovery process. If the error recovery process fails, a seek positioning error (Error code = 15h or 02h) will be reported with a Hardware error (04h) in the Sense Key. Recoverable seek errors are specified at Less than 10 errors in 108 seeks. Unrecoverable seek errors (Sense Key = 04h) are classified as drive failures.

5.1.4Interface errors

An interface error is defined as a failure of the receiver on a port to recover the data as transmitted by the device port connected to the receiver. The error may be detected as a running disparity error, illegal code, loss of word sync, or CRC error. The total error rate for a loop of devices is the sum of the individual device error rates.

5.2Reliability and service

You can enhance the reliability of Cheetah K15.4 disc drives by ensuring that the drive receives adequate cool- ing. Section 6.0 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.

5.2.1Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF)

These drives shall achieve an AFR of 0.62% (MTBF of 1,400,000 hours) when operated in an environment that ensures the HDA case temperatures do not exceed the values specified in Section 6.4.1.

Operation at case temperatures outside the specifications in Section 6.4.1 may increase the AFR (decrease the MTBF). AFR and MTBF statistics are poplulation statistics that are not relevant to individual units.

AFR and MTBF specifications are based on the following assumptions for Enterprise Storage System environ- ments:

•8,760 power-on hours per year

•250 average on/off cycles per year

•Operating at nominal voltages

•System provides adequate cooling to ensure the case temperatures specified in Section 6.4.1 are not exceeded.

5.2.2Preventive maintenance

No routine scheduled preventive maintenance is required.

5.2.3Hot plugging the drive

Inserting and removing the drive on the FC-AL will interrupt loop operation. The interruption occurs when the receiver of the next device in the loop must synchronize to a different input signal. FC error detection mecha- nisms, character sync, running disparity, word sync, and CRC are able to detect any error. Recovery is initiated based on the type of error.

The disc drive defaults to the FC-AL Monitoring state, Pass-through state, when it is powered-on by switching the power or hot plugged. The control line to an optional port bypass circuit (external to the drive), defaults to the Enable Bypass state. If the bypass circuit is present, the next device in the loop will continue to receive the output of the previous device to the newly inserted device. If the bypass circuit is not present, loop operation is temporarily disrupted until the next device starts receiving the output from the newly inserted device and regains synchronization to the new input.

16 Cheetah 15K.5 FC Product Manual, Rev. D