Product manual

Cheetah 4LP FC Product Manual, Rev. A 13
5.0 Reliability specifications
The following reliability specifications assume correct host and drive operational interface, including all inter-
face timings, power supply voltages, and environmental requirements.
5.1 Error rates
The error rates stated in this manual assume the following:
• The drive is operated in accordance with this manual using DC power as defined in paragraph 6.2, “DC
power requirements.”
• The drive has been formatted with the FC-AL format commands.
• Errors caused by media defects or host system failures are excluded from error rate computations.
5.1.1 Environmental interference
When evaluating systems operation under conditions of electromagnetic interference (EMI), the performance
of the drive within the system is considered acceptable if the drive does not generate an unrecoverable condi-
tion.
An unrecoverable error, or condition, is defined as one that:
• is not detected and corrected by the drive itself, or
• is not detected from the error or fault status provided through the drive or FC-AL interface, or
• is not recovered by normal drive or system recovery procedures without operator intervention.
5.1.2 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.
5.1.3 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 that 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 must be no
more than ten recoverable seek errors in 10
8
physical seek operations. After detecting an initial seek error, the
drive automatically reseeks to the addressed track up to three 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 (01h). If all three reseeks fail, a seek positioning error (15h) is reported
Seek error rate:
Less than 10 errors in 10
8
seeks
Recoverable media error rate
(using default settings):
Less than 10 errors in 10
11
bits transferred
Unrecovered media data:
Less than 1 sector in 10
14
bits transferred
Miscorrected media data:
Less than 1 sector in 10
21
bits transferred
Interface error rate:
Less than 1 error in 10
12
bits transferred with minimum receive eye.
Less than 1 error in 10
14
bits transferred with typical receive eye.
See Section 9.6.4, “Differential PECL input.”
MTBF: 1,000,000 hours
Service life: 5 years
Preventive maintenance: None required