Maxtor D740X-6L 20.0 AT, Руководство по эксплуатации продукта

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Basic Principles of Operation
Maxtor D740X-6L 20.0/40.0/60.0/80.0GB AT 5-14
of up to 150 bits within one sector can be corrected “on-the-fly,” in real time as they
occur, allowing a high degree of data integrity with no impact on the drive’s
performance.
The drive does not need to re-read a sector on the next disk revolution or apply ECC
for those errors that are corrected on-the-fly. Errors corrected in this manner are
invisible to the host system.
When errors cannot be corrected on-the-fly, an automatic retry, and a more rigorous
16 10-bit symbols error correction algorithm enables the correction of any sector with
single bursts (up to 16 contiguous 10-bit symbols), or up to 16 multiple random one
10-bit symbol burst errors. In addition to this error correction capability, the drive’s
implementation of an additional cross-checking code and algorithm double checks the
main ECC correction, and greatly decreases the likelihood of miscorrection.
The 32 ECC check symbols shown in Figure 5-4 are used to detect and correct errors.
The cross-checking and ECC data is computed and appended to the user data when
the sector is first written.
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Sector Data Field with ECC Check Bytes
Because the ECC check symbols follow the cross checking bytes, errors found within
the cross-checking bytes can be corrected. Due to the power and sophistication of the
code, errors found within the ECC check bytes can also be corrected.
Each time a sector of data is read, the Maxtor D740X-6L drives will generate a new
set of ECC check symbols and cross-checking bytes from the user data. These new
check symbols are compared to the ones originally written to the disk. The difference
between the newly computed and original check symbols is reflected in a set of 32
syndromes and three cross checking syndromes, which correspond to the number of
check symbols. If all the ECC syndrome values equal zero, and cx syndrome value
equals zero or 0FF, the data was read with no errors, and the sector is transferred to
the host system. If any of the syndromes do not equal zero or OFF, an error has
occurred. The type of correction the drive applies depends on the nature and the
extent of the error.
High speed on-the-fly error correction saves several milliseconds because there is no
need to wait for a disk revolution to bring the sector under the head for re-reading.