HP Surestore 160ex - Optical Jukebox, Руководство по обслуживанию

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Theory of Operation
Optical Drive Mechanism
Chapter 6 6-24
number, and a Cyclic Redundancy Check (CRC). The error threshold is
determined by the number of sectors found “good.”
The other error threshold of interest pertains to the degree of error
correction required on the data. The error correction code (ECC) used
causes parity bytes to be written following the user data. During a data
recovery operation, these bytes are used to detect and correct up to 8
defective bytes in an interleave. Each sector has 10 (5) interleaves with
120 (122) bytes in each interleave. The actual number of bytes per
interleave requiring correction is used as an error threshold. Consult the
ISO standard for more details.
The table on the next page shows the error thresholds for the optical
drive. The sector IDs column refers to the minimum number of sector IDs
that must be read correctly for the corresponding operation to be deemed
successful. The ECC level column refers to the to the maximum number
of bytes per interleave that require correction in order for the
corresponding operation to be deemed successful.
Error Detection
The jukebox error detection methods are extensive. Both processes and
sensors detect errors.
Each of the processes that detect errors are interrelated. Depending on
the error condition, the jukebox expects feedback from one or more of the
following processes before a diagnosis is made:
• Overforce shutdown : An overforce shutdown occurs when the
motors exert more force than is expected or required. If this occurs,
the servo automatically shuts itself down to prevent parts damage.
Operation Sector IDs ECC Level
Format 1 3
Write 2 -
Erase 2 -
Verify 2 4
Read
(recovered) 1 7
Read 1 8