Cheetah 36XL Product Manual, Rev. E | 15 |
5.0Reliability 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).
Seek Errors
Read Error Rates [1]
Recovered Data
Unrecovered Data
Miscorrected Data
MTBF
Service Life
Preventive Maintenance
Note.
[1]Error rate specified with automatic retries and data correction with ECC enabled and all flaws reallocated.
5.1Error 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.
5.1.1Environmental 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.
5.1.2Read 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.
5.1.3Write 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).
5.1.4Seek 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 108 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