Cheetah X15 36LP Product Manual, Rev. D
13
5.0
Reliability specifications
The following reliability specifications assume correct host/drive operational interface, including all interface
timings, power supply voltages, environmental requirements and drive mounting constraints (see Section 8.4).
Note.
[1]
Error rate specified with automatic retries and data correction with ECC enabled and all flaws reallocated.
5.1
Error rates
The error rates stated in this specification assume the following:
• The drive is operated per this specification using DC power as defined in this manual (see Section 6.2).
• The drive has been formatted with the SCSI FORMAT command.
• Errors caused by media defects or host system failures are excluded from error rate computations. Refer to
Section 3.2, “Media Characteristics.”
• Assume random data.
5.1.1
Environmental interference
When evaluating systems operation under conditions of Electromagnetic Interference (EMI), the performance
of the drive within the system shall be considered acceptable if the drive does not generate an unrecoverable
condition.
An unrecoverable error, or unrecoverable condition, is defined as one that:
• Is not detected and corrected by the drive itself;
• Is not capable of being detected from the error or fault status provided through the drive or SCSI interface; or
• Is not capable of being recovered by normal drive or system recovery procedures without operator interven-
tion.
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
8
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
Seek Errors
Less than 10 in 10
8
seeks
Read Error Rates [1]
Recovered Data
Less than 10 errors in 10
12
bits transferred (OEM default settings)
Unrecovered Data
Less than 1 sector in 10
15
bits transferred (OEM default settings)
Miscorrected Data
Less than 1 sector in 10
21
bits transferred
MTBF
1,200,000 hours
Service Life
5 years
Preventive Maintenance
None required
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