Computer Drive User Manual

16 Cheetah NS 10K.2 FC Product Manual, Rev. B
5.1.3 Seek 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 10
8
seeks. Unrecoverable seek errors
(Sense Key = 04h) are classified as drive failures.
5.1.4 Interface 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.
5.2 Reliability and service
You can enhance the reliability of disk drives by ensuring that the drive receives adequate cooling. 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.
5.2.1 Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF)
These drives shall achieve an AFR of 0.55% (MTBF of 1,600,000 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 environments:
• 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.
5.2.2 Preventive maintenance
No routine scheduled preventive maintenance is required.
5.2.3 Hot 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 disk 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.